Retransmission methods including discontinuous transmission and related devices

ABSTRACT

A method of operating a node of a radio access network may include transmitting first and second data blocks from the radio access network over respective first and second MIMO layers of a MIMO wireless channel to a wireless terminal during a first TTI. Responsive to receiving a NACK message for the second data block, downlink signaling for a second TTI may be transmitted from the radio access network to the wireless terminal with the downlink signaling including a DTX indicator for the first MIMO layer and a retransmission data indicator for the second MIMO layer. Responsive to receiving the NACK message for the second data block, the second data block may be retransmitted from the radio access network over the second MIMO layer to the wireless terminal during a second TTI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part under 35 U.S.C. 111(a) of PCTApplication No. PCT/SE2013/050488, filed May 3, 2013, which in turnclaims the benefit of under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication Ser. No. 61/682,547, filed Aug. 13, 2012, U.S. ProvisionalApplication No. 61/694,519, filed Aug. 29, 2012, and U.S. ProvisionalApplication No. 61/702,373, filed Sep. 18, 2012, the disclosures of eachof which are incorporated by reference herein in their entireties.

This application is a continuation-in-part under 35 U.S.C. 111(a) of PCTApplication No. PCT/SE2013/050486, filed May 3, 2013, which in turnclaims the benefit of under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication Ser. No. 61/682,547, filed Aug. 13, 2012, U.S. ProvisionalApplication No. 61/694,519, filed Aug. 29, 2012, and U.S. ProvisionalApplication No. 61/702,373, filed Sep. 18, 2012, the disclosures of eachof which are incorporated by reference herein in their entireties.

This application is a continuation-in-part under 35 U.S.C. 111(a) of PCTApplication No. PCT/SE2013/050487, filed May 3, 2013, which in turnclaims the benefit of under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication Ser. No. 61/682,547, filed Aug. 13, 2012, U.S. ProvisionalApplication No. 61/694,519, filed Aug. 29, 2012, and U.S. ProvisionalApplication No. 61/702,373, filed Sep. 18, 2012, the disclosures of eachof which are incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present disclosure is directed to wireless communications and, moreparticularly, to multiple-input-multiple-output (MIMO) wirelesscommunications and related network nodes and wireless terminals.

BACKGROUND

In a typical cellular radio system, wireless terminals (also referred toas user equipment unit nodes, UEs, and/or mobile stations) communicatevia a radio access network (RAN) with one or more core networks. The RANcovers a geographical area which is divided into cell areas, with eachcell area being served by a radio base station (also referred to as aRAN node, a “NodeB”, and/or enhanced NodeB “eNodeB”). A cell area is ageographical area where radio coverage is provided by the base stationequipment at a base station site. The base stations communicate throughradio communication channels with UEs within range of the base stations.

Moreover, a cell area for a base station may be divided into a pluralityof sectors surrounding the base station. For example, a base station mayservice three 120 degree sectors surrounding the base station, and thebase station may provide a respective directional transceiver and sectorantenna array for each sector. Stated in other words, a base station mayinclude three directional sector antenna arrays servicing respective 120degree base station sectors surrounding the base station.

Multi-antenna techniques can significantly increase capacity, datarates, and/or reliability of a wireless communication system asdiscussed, for example, by Telatar in “Capacity Of Multi-AntennaGaussian Channels” (European Transactions On Telecommunications, Vol.10, pp. 585-595, November 1999). Performance may be improved if both thetransmitter and the receiver for a base station sector are equipped withmultiple antennas (e.g., an sector antenna array) to provide amultiple-input multiple-output (MIMO) communication channel(s) for thebase station sector. Such systems and/or related techniques are commonlyreferred to as MIMO. The LTE standard is currently evolving withenhanced MIMO support and MIMO antenna deployments. A spatialmultiplexing mode is provided for relatively high data rates in morefavorable channel conditions, and a transmit diversity mode is providedfor relatively high reliability (at lower data rates) in less favorablechannel conditions.

In a downlink from a base station transmitting from a sector antennaarray over a MIMO channel to a wireless terminal in the sector, forexample, spatial multiplexing (or SM) may allow the simultaneoustransmission of multiple symbol streams over the same frequency from thebase station sector antenna array for the sector. Stated in other words,multiple symbol streams may be transmitted from the base station sectorantenna array for the sector to the wireless terminal over the samedownlink time/frequency resource element (TFRE) to provide an increaseddata rate. In a downlink from the same base station sector transmittingfrom the same sector antenna array to the same wireless terminal,transmit diversity (e.g., using space-time codes) may allow thesimultaneous transmission of the same symbol stream over the samefrequency from different antennas of the base station sector antennaarray. Stated in other words, the same symbol stream may be transmittedfrom different antennas of the base station sector antenna array to thewireless terminal over the same time/frequency resource element (TFRE)to provide increased reliability of reception at the wireless terminaldue to transmit diversity gain.

Four layer MIMO transmission schemes are proposed forHigh-Speed-Downlink-Packet-Access (HSDPA) within Third GenerationPartnership Project (3GPP) standardization. Accordingly, up to 4 channelencoded transport data blocks (sometimes referred to as transport datablock codewords) may be transmitted using a same TFRE when using4-branch MIMO transmission. Because ACK/NACK signaling and/or channelencoding for each transport data block to be transmitted during a sameTFRE may require wireless terminal feedback (e.g., as ACK/NACK and/orCQI or channel quality information), feedback to define ACK/NACK and/orchannel encoding for 4 transport data blocks may be required when using4-branch MIMO transmission. Feedback signaling when using 4-branch MIMOtransmission may thus be undesirably high, for example, becausedifferent MIMO layers may be received at a wireless terminal during asame TFRE with different qualities, signal strengths, error rates, etc.

SUMMARY

It may therefore be an object to address at least some of the abovementioned disadvantages and/or to improve performance in a wirelesscommunication system. Some embodiments discussed herein, for example,may provide improved HARQ retransmission gain(s) without significantlyincreasing delay(s).

According to some embodiments, a method of operating a node of a radioaccess network may include transmitting first and second data blocksfrom the radio access network over respective first and secondmultiple-input-multiple-output (MIMO) layers of a MIMO wireless channelto a wireless terminal during a first transmission time interval (TTI).Responsive to receiving a negative acknowledgment (NACK) message for thesecond data block, downlink signaling for a second TTI may betransmitted from the radio access network to the wireless terminal withthe downlink signaling including a discontinuous transmission (DTX)indicator for the first MIMO layer and a retransmission data indicatorfor the second MIMO layer. Responsive to receiving the negativeacknowledgment (NACK) message for the second data block, the second datablock may be retransmitted from the radio access network over the secondMIMO layer to the wireless terminal during a second TTI.

By using a discontinuous transmission indicator, communication and/orprocessing resources may be conserved at the radio access network and/orat the wireless terminal while supporting retransmission ofnon-acknowledged data. The radio access network, for example, mayretransmit the previously non-acknowledged data of a first MIMOstream(s)/layer(s) without devoting significant resources totransmission/processing of another MIMO stream(s)/layer(s) subject todiscontinuous transmission.

Transmitting the downlink signaling may include transmitting thedownlink signaling responsive to receiving an acknowledgment (ACK)message for the first data block and responsive to receiving thenegative acknowledgment (NACK) message for the second data block, andretransmitting the second data block may include retransmitting thesecond data block responsive to receiving the acknowledgment (ACK)message for the first data block and responsive to receiving thenegative acknowledgment (NACK) message for the second data block.

Retransmitting the second data block during the second TTI may includeretransmitting the second data block without transmitting data over thefirst MIMO layer during the second TTI.

Before transmitting the first and second data blocks during the firsttransmission time interval, first and second HARQ processidentifications may be selected for the first and second MIMO layers,and before transmitting the downlink signaling for the second TTI, aHARQ-DTX process identification may be generated for the first MIMOlayer as a function of the second HARQ process identification for thesecond MIMO layer.

Transmitting the downlink signaling may include transmitting thedownlink signaling responsive to receiving first and second negativeacknowledgment (NACK) messages for the first and second data blocks, andretransmitting the second data block may include retransmitting thesecond data block responsive to receiving the first and second negativeacknowledgment (NACK) messages for the first and second data blocks. Inresponse to receiving two NACK messages, the radio access network maythus use discontinuous transmission over one of the MIMO streams/layers(e.g., not transmitting one of the NACKed data block or blocks) toreduce inter-layer interference relative to the other data block(s) thatis retransmitted over the other MIMO stream(s)/layer(s). Accordingly, alikelihood of the retransmitted data block(s) being successfullyreceived/decoded at the wireless terminal may be improved during theretransmission.

Retransmitting the second data block during the second TTI may includeretransmitting the second data block without transmitting data over thefirst MIMO layer during the second TTI.

Responsive to receiving an acknowledgment (ACK) message for theretransmission of the second data block during the second TTI, downlinksignaling may be transmitted from the radio access network to thewireless terminal for a third TTI wherein the downlink signaling for thethird TTI includes a discontinuous transmission (DTX) indicator for thesecond MIMO layer and a retransmission data indicator for the first MIMOlayer. Responsive to receiving the acknowledgment (ACK) message for theretransmission of the second data block during the second TTI, the firstdata block may be retransmitted from the radio access network over thefirst MIMO layer to the wireless terminal during the third TTI.

Before transmitting the first and second data blocks during the firsttransmission time interval, first and second HARQ processidentifications may be selected for the first and second MIMO layers,and before transmitting the downlink signaling for the second TTI,generating a HARQ-DTX process identification may be generated for thefirst MIMO layer as a function of the second HARQ process identificationfor the second MIMO layer.

Transmitting the first and second data blocks may include transmittingthe first and second data blocks in accordance with a first MIMO rank.Transmitting the downlink signaling may include transmitting thedownlink signaling responsive to receiving the negative acknowledgment(NACK) message for the second data block and responsive to receiving apreference for a second MIMO rank less than the first rank from thewireless terminal. Moreover, retransmitting the second data block mayinclude retransmitting the second data block during the second TTI inaccordance with the first MIMO rank responsive to receiving the negativeacknowledgment (NACK) message for the second data block and responsiveto receiving the preference for the second MIMO rank less than the firstMIMO rank. By maintaining the same rank for a retransmission even thoughthe wireless terminal has requested a lower rank, a mapping of MIMOlayers and soft buffers may be maintained to support combination ofsymbols/bits of previous transmissions and retransmissions of the seconddata block.

Moreover, transmitting the downlink signaling may include transmittingthe downlink signaling responsive to receiving a negative acknowledgment(NACK) for the first data block, responsive to receiving the negativeacknowledgment (NACK) message for the second data block, and responsiveto receiving the preference for the second MIMO rank less than the firstrank.

Responsive to receiving an acknowledgment (ACK) message for theretransmission of the second data block during the second TTI, downlinksignaling may be transmitted from the radio access network to thewireless terminal for a third TTI with the downlink signaling for thethird TTI including a retransmission data indicator for the first MIMOlayer and a discontinuous transmission (DTX) indicator for the secondMIMO layer. Responsive to receiving the acknowledgment (ACK) message forthe retransmission of the second data block during the second TTI, thefirst data block may be retransmitted from the radio access network overthe second MIMO layer to the wireless terminal during the third TTI inaccordance with the first MIMO rank.

Before transmitting the first and second data blocks during the firsttransmission time interval, first and second HARQ processidentifications may be selected for the first and second MIMO layers,and before transmitting the downlink signaling for the second TTI, aHARQ-DTX process identification may be generated for the first MIMOlayer as a function of the second HARQ process identification for thesecond MIMO layer.

Retransmitting the second data block during the second TTI may includeretransmitting the second data block without transmitting data over thefirst MIMO layer during the second TTI.

First and second HARQ process identifications may be selected for firstand second MIMO layers. Responsive to selecting the first and secondHARQ process identifications, downlink signaling may be transmitted fromthe radio access network to the wireless terminal for the firsttransmission time interval (TTI). Responsive to receiving the negativeacknowledgment (NACK) message for the second data block, a HARQdiscontinuous transmission (DTX) process identification may be generatedfor the first MIMO layer as a function of the second HARQ processidentification for the second MIMO layer. Transmitting the downlinksignaling for the second TTI may include transmitting the downlinksignaling for the second TTI responsive to generating the HARQ-DTXprocess identification and responsive to receiving the NACK message forthe second data block. Retransmitting the second data block may includeretransmitting the second data block responsive to generating theHARQ-DTX process identification and responsive to receiving the NACKmessage for the second data block.

According to some other embodiments, a node of a radio access networkmay include a transceiver configured to communicate with a wirelessterminal over a multiple-input-multiple-output (MIMO) wireless channel,and a processor coupled to the transceiver, the processor may beconfigured to transmit first and second data blocks through thetransceiver over respective first and second MIMO layers of the MIMOwireless channel to a wireless terminal during a first transmission timeinterval (TTI). The processor may be configured to transmit downlinksignaling for a second TTI through the transceiver to the wirelessterminal responsive to receiving a negative acknowledgment (NACK)message for the second data block, with the downlink signaling includinga discontinuous transmission (DTX) indicator for the first MIMO layerand a retransmission data indicator for the second MIMO layer. Theprocessor may be configured to retransmit the second data block throughthe transceiver over the second MIMO layer to the wireless terminalduring a second TTI responsive to receiving the negative acknowledgment(NACK) message for the second data block.

The processor may be configured to transmit the downlink signalingresponsive to receiving an acknowledgment (ACK) message for the firstdata block and responsive to receiving the negative acknowledgment(NACK) message for the second data block, and the processor may beconfigured to retransmit the second data block responsive to receivingthe acknowledgment (ACK) message for the first data block and responsiveto receiving the negative acknowledgment (NACK) message for the seconddata block.

The processor may be configured to transmit the downlink signalingresponsive to receiving first and second negative acknowledgment (NACK)messages for the first and second data blocks, and the processor may beconfigured to retransmit the second data block responsive to receivingthe first and second negative acknowledgment (NACK) messages for thefirst and second data blocks.

The processor may be configured to transmit the first and second datablocks in accordance with a first MIMO rank. The processor may beconfigured to transmit the downlink signaling responsive to receivingthe negative acknowledgment (NACK) message for the second data block andresponsive to receiving a preference for a second MIMO rank less thanthe first rank from the wireless terminal. The processor is configuredto retransmit the second data block by retransmitting the second datablock during the second TTI in accordance with the first MIMO rankresponsive to receiving the negative acknowledgment (NACK) message forthe second data block and responsive to receiving the preference for thesecond MIMO rank less than the first MIMO rank.

The processor may also be configured to select first and second HARQprocess identifications for first and second MIMO layers, to transmitdownlink signaling from the radio access network to the wirelessterminal for the first transmission time interval (TTI) responsive toselecting the first and second HARQ process identifications, and togenerate a HARQ discontinuous transmission (DTX) process identificationfor the first MIMO layer as a function of the second HARQ processidentification for the second MIMO layer responsive to receiving thenegative acknowledgment (NACK) message for the second data block. Inaddition, the processor may be configured to transmit the downlinksignaling for the second TTI responsive to generating the HARQ-DTXprocess identification and responsive to receiving the NACK message forthe second data block, and to retransmit the second data blockresponsive to generating the HARQ-DTX process identification andresponsive to receiving the NACK message for the second data block.

The processor may be configured to retransmit the second data blockwithout transmitting data over the first MIMO layer during the secondTTI.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate certain non-limiting embodiment(s).In the drawings:

FIG. 1 is a block diagram of a communication system that is configuredaccording to some embodiments;

FIG. 2 is a block diagram illustrating a base station and a wirelessterminal according to some embodiments of FIG. 1;

FIG. 3A is a message sequence chart for a MIMO communication system;

FIG. 3B is illustrates a feedback channel report format of FIG. 3A;

FIG. 4 is a block diagram illustrating elements/functionalities of basestation processors according to some embodiments of FIG. 2;

FIG. 5 is a block diagram illustrating elements/functionalities ofwireless terminal processors according to some embodiments of FIG. 2;

FIG. 6 illustrates schematically a medium access control (MAC) entity ina wireless terminal (UE);

FIGS. 7A and 7B are tables illustrating combinations of sharing HARQprocesses between multiple MIMO data streams for rank/layer 3 and 4 MIMOtransmissions;

FIGS. 8A and 8B are flow charts illustrating operations of base stationsand wireless terminals according to some embodiments;

FIG. 9 is a flow chart illustrating base station operations according tosome embodiments;

FIGS. 10, 11, 12, and 13 are tables illustrating MIMO rank selectionaccording to some embodiments;

FIG. 14 is a table illustrating allocations of two HARQ processes toMIMO data layers/streams for rank 1, 2, 3, and 4 MIMOtransmission/reception according to some other embodiments;

FIGS. 15, 16, 17, and 18 are tables illustrating MIMO rank selectionaccording to some embodiments;

FIG. 19 is a flow chart illustrating operations for retransmissionsaccording to some other embodiments;

FIGS. 20A, 20B, and 20C are tables illustrating retransmission fordifferent ranks according to embodiments of FIG. 21;

FIGS. 21A, 21B, 21C, and 21D are block diagrams illustrating downlinksignaling structures according some embodiments;

FIGS. 22 and 23 are tables illustrating modulation and rank bit patternsaccording to some embodiments;

FIG. 24 is a flow chart illustrating operations of a wireless terminalprocessor according to some embodiments; and

FIGS. 25, 26, and 27 illustrate operations of a base station processoraccording to some embodiments.

DETAILED DESCRIPTION

Inventive concepts will now be described more fully hereinafter withreference to the accompanying drawings, in which examples of embodimentsare shown. These inventive concepts may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of present inventive concepts to those skilled in theart. It should also be noted that these embodiments are not mutuallyexclusive. Components from one embodiment may be tacitly assumed to bepresent/used in another embodiment.

For purposes of illustration and explanation only, these and otherembodiments are described herein in the context of operating in a RANthat communicates over radio communication channels with wirelessterminals (also referred to as UEs). It will be understood, however,that present inventive concepts are not limited to such embodiments andmay be embodied generally in any type of communication network. As usedherein, a wireless terminal (also referred to as a UE) can include anydevice that receives data from a communication network, and may include,but is not limited to, a mobile telephone (“cellular” telephone),laptop/portable computer, pocket computer, hand-held computer, and/ordesktop computer.

In some embodiments of a RAN, several base stations can be connected(e.g., by landlines or radio channels) to a radio network controller(RNC). The radio network controller, also sometimes termed a basestation controller (BSC), supervises and coordinates various activitiesof the plural base stations connected thereto. The radio networkcontroller is typically connected to one or more core networks.

The Universal Mobile Telecommunications System (UMTS) is a thirdgeneration mobile communication system, which evolved from the GlobalSystem for Mobile Communications (GSM), and is intended to provideimproved mobile communication services based on Wideband Code DivisionMultiple Access (WCDMA) technology. UTRAN, short for UMTS TerrestrialRadio Access Network, is a collective term for the Node B's and RadioNetwork Controllers which make up the UMTS radio access network. Thus,UTRAN is essentially a radio access network using wideband code divisionmultiple access for UEs.

The Third Generation Partnership Project (3GPP) has undertaken tofurther evolve the UTRAN and GSM based radio access networktechnologies. In this regard, specifications for the Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) are ongoing within 3GPP. TheEvolved Universal Terrestrial Radio Access Network (E-UTRAN) comprisesthe Long Term Evolution (LTE) and System Architecture Evolution (SAE).

Note that although terminology from 3GPP (3^(rd) Generation PartnershipProject) LTE (Long Term Evolution) is used in this disclosure toexemplify embodiments of inventive concepts, this should not be seen aslimiting the scope of inventive concepts to only these systems. Otherwireless systems, including WCDMA (Wideband Code Division MultipleAccess), WiMax (Worldwide Interoperability for Microwave Access), UMB(Ultra Mobile Broadband), HSDPA (High-Speed Downlink Packet Access), GSM(Global System for Mobile Communications), etc., may also benefit fromexploiting embodiments disclosed herein.

Also note that terminology such as base station (also referred to aseNodeB or Evolved Node B) and wireless terminal (also referred to as UEor User Equipment) should be considering non-limiting and does not implya certain hierarchical relation between the two. In general a basestation (e.g., an “eNodeB”) and a wireless terminal (e.g., a “UE”) maybe considered as examples of respective different communications devicesthat communicate with each other over a wireless radio channel. Whileembodiments discussed herein may focus on wireless transmissions in adownlink from an eNodeB to a UE, embodiments of inventive concepts mayalso be applied, for example, in the uplink.

FIG. 1 is a block diagram of a communication system that is configuredto operate according to some embodiments of present inventive concepts.An example RAN 60 is shown that may be a Long Term Evolution (LTE) RAN.Radio base stations (e.g., eNodeBs) 100 may be connected directly to oneor more core networks 70, and/or radio base stations 100 may be coupledto core networks 70 through one or more radio network controllers (RNC).In some embodiments, functionality of a radio network controller(s) maybe performed by radio base stations 100. Radio base stations 100communicate over wireless channels 300 with wireless terminals (alsoreferred to as user equipment nodes or UEs) 200 that are within theirrespective communication service cells (also referred to as coverageareas). The radio base stations 100 can communicate with one anotherthrough an X2 interface and with the core network(s) 70 through S1interfaces, as is well known to one who is skilled in the art.

FIG. 2 is a block diagram of a base station 100 and a wireless terminal200 of FIG. 1 in communication over wireless channel 300 according tosome embodiments of present inventive concepts. As shown, base station100 may include transceiver 109 coupled between processor 101 andantenna array 117 (including multiple antennas), and memory 118 coupledto processor 101. Moreover, wireless terminal 200 may includetransceiver 209 coupled between antenna array 217 and processor 201, anduser interface 221 and memory 218 may be coupled to processor 201.Accordingly, base station processor 101 may transmit communicationsthrough transceiver 109 and antenna array 117 for reception at wirelessterminal processor 201 through antenna array 217 and transceiver 209. Inthe other direction, wireless terminal processor 201 may transmitcommunications through transceiver 209 and antenna array 217 forreception at base station processor 101 through antenna array 117 andtransceiver 109. To support up to 4-branch MIMO (allowing paralleltransmission of 4 layers/streams of data using a same TFRE), each ofantenna arrays 117 and 217 may include four (or more) antenna elements.Wireless terminal 200 of FIG. 2, for example, may be a cellularradiotelephone, a smart phone, a laptop/netbook/tablet/handheldcomputer, or any other device providing wireless communications. Userinterface 211, for example, may include a visual display such as anliquid crystal display, a touch sensitive visual display, a keypad, aspeaker, a microphone, etc.

For MIMO downlink transmissions from RAN 60 to wireless terminal 200, acodebook of precoding vectors (known at both RAN 60 and wirelessterminal 200) is used to precode (e.g., to apply precoding weights to)the different data layers (data streams) that are transmitted inparallel from a sector antenna array(s) to the wireless terminal 200during a same TFRE, and to decode the data layers (data streams)received in parallel during the same TFRE at wireless terminal 200. Thesame codebook of precoding vectors may be stored in wireless terminalmemory 218 and in base station memory 118. Moreover, wireless terminal200 may estimate characteristics of each downlink channel to generatechannel quality information (CQI), and CQI feedback from wirelessterminal 200 may be transmitted to base station 100. This CQI feedbackmay then be used by the base station processor 101 to select:transmission rank (i.e., a number of data layers/streams to betransmitted during a subsequent TFRE); transport data block length(s);channel code rate(s) to be used to channel encode different transportdata blocks; modulation order(s); symbol to layer mapping schemes;and/or precoding vectors for respective downlink transmissions to thewireless terminal 200.

By way of example, base station antenna array 117 may include 4 antennasand wireless terminal antenna array 217 may include four antennas sothat wireless terminal 200 may receive up to four downlink data layers(data streams) from base station antenna array 117 during MIMOcommunications. In this example, the precoding codebook may include rank1 precoding vectors (used when transmitting one downlink data streamfrom a base station sector antenna array 117 to wireless terminal 200),rank 2 precoding vectors (used when transmitting two downlink datastreams from a base station sector antenna array 117 to wirelessterminal 200), rank 3 precoding vectors (used when transmitting threedownlink data streams from a base station sector antenna array 117 towireless terminal 200), and rank 4 precoding vectors (used whentransmitting four downlink data streams from a base station sectorantenna array 117 to wireless terminal 200). Precoding vectors may alsobe referred to, for example, as precoding codebook entries, precodingcodewords, and/or precoding matrices.

An issue for four layer MIMO transmission schemes for HSDPA is whatnumber of HARQ (Hybrid Automatic Repeat Request) codewords/processesshould be supported. To reduce uplink and/or downlink signaling, twoHARQ codewords/processes may be used in four layer MIMO transmissionschemes for feedback relating to one, two, three, and four layerdownlink transmissions. Use of two HARQ codewords/processes may berelatively easier to implement without significantly reducingperformance (relative to use of four HARQ codewords/processes).

A Hybrid Automatic Repeat Request (HARQ) process(es) may be used in awireless system to overcome transmission errors that cannot be correctedusing a forward error correction code (also referred to as a channelcode) alone. In some embodiments of a HARQ process, the HARQ process ismapped to one or more MIMO transmission layers, and the transmittingdevice (e.g., base station 100) attaches an error detection/correctioncode (e.g., a cyclic redundancy check or CRC code) to each transportdata block (also referred to as a data block, data packet, packet, etc.)of a TTI/TFRE to provide error detection/correction. At the receivingdevice (e.g., at wireless terminal 200), the contents of each receivedtransport data block may be validated using the respective errordetection/correction code attached thereto. If the transport data blockfails the error detection/correction validation, the receiving devicemay send a HARQ codeword including a negative acknowledgement NACKmessage (also referred to as a non-acknowledgement message) for the HARQprocess back to the transmitting device to request a retransmission ofthe failed transport data block or blocks mapped to the HARQ process. Afailed data block may be retransmitted until it is either decoded oruntil a maximum number of allowed retransmissions (e.g., four to sixretransmissions) have occurred. If the transport data block passes theerror detection/correction validation, a HARQ codeword including anacknowledgement ACK message is sent back to the transmitting device toacknowledge reception and correct decoding of the transport data block.A HARQ process may thus be mapped to one or more MIMO transmissionlayers, and for each TTI/TFRE, the HARQ process may generate a HARQACK/NACK feedback message that is transmitted in a HARQ codeword of thefeedback channel (e.g., HS-PDCCH).

As discussed in greater detail below, a wireless terminal 200implementing HARQ functionality may include a soft buffer for eachtransport data block received during a TFRE so that originallytransmitted and retransmitted transport data blocks may be combinedbefore decoding to thereby improve system throughput. Depending on theway the originally transmitted and retransmitted transport data blocksare combined, HARQ systems/processes may be classified as chasecombining or CC (retransmitting the same transport data block withoutadditional information) or Incremental Redundancy or IR (transmittingthe same transport data block with additional parity bits).

A single soft buffer may be used for layer/rank one MIMOtransmission/reception (with one transport data block received during aTFRE), two soft buffers may be used for layer/rank two MIMOtransmission/reception (with two transport data blocks received during aTFRE), three soft buffers may be used for layer/rank three MIMOtransmission/reception (with three transport data blocks received duringa TFRE), and four soft buffers may be used for layer/rank four MIMOtransmission/reception (with four transport data blocks received duringa TFRE). Each soft buffer stores a demodulator output for a transportdata block before decoding to be used after a retransmission if thetransport data block is not successfully decoded. For Release 7 MIMOsupporting up to two rank/layer transmissions (with up to two transportdata blocks transmitted to a UE during a TFRE), a HARQ process isprovided for each soft buffer and thus for each transport data block.When two HARQ processes are mapped to three or four layer/rank MIMOtransmission/reception, however, a mechanism to map UE receiver softbuffers to HARQ processes may be needed.

According to some embodiments discussed herein, methods may be providedto map functionalities between base station 100 transmission layers,wireless terminal 200 receiver layers (including respective softbuffers), and HARQ processes for situations when the number of supportedHARQ processes is less than a number of MIMO transmission layers/rankssupported by the system (e.g., when rank/layer 3 and/or 4 MIMOtransmissions are supported but only two HARQ processes are supported).With two HARQ processes, both HARQ ACK/NACK messages may be included ina HARQ codeword of the feedback channel (e.g., HS-DPCCH).

FIG. 3A illustrates a message sequence between base station 100 andwireless terminal 200 in a MIMO communications system. As shown in FIG.3A, base station 100 transmits pilot signals over the downlinkchannel(s), and wireless terminal 200 estimates the downlink channel(s)at block 391 (for transmissions from base station 100 to wirelessterminal 200) based on the pilot signals. Wireless terminal 200generates (e.g., computes) channel state information at block 393 forthe downlink channel(s), and wireless terminal 200 reports the channelstate information to base station 100 over a feedback channel. Anexample of a format for a feedback channel report for two reportingintervals is illustrated in FIG. 3B, and FIG. 3B shows that the feedbackchannel report may include a HARQ element/message/codeword (includingacknowledge/ACK and/or negative-acknowledge/NACK information) and/orCQI/PCI (channel quality information and/or precoding control indicator)information.

More particularly, wireless terminal 200 may transmit CQI/PCIinformation (over the feedback channel) including a rank indicatorrequesting/recommending a MIMO transmission rank for subsequent downlinktransmissions from base station 100 to wireless terminal 200. Basestation processor 101 may select the requested/recommended MIMO rank ora different MIMO rank, and base station 100 may identify the selectedMIMO rank in downlink signaling transmitted to wireless terminal 200,for example, using a downlink signaling channel HS-SCCH (High-SpeedShared Control Channel). Base station 100 may then transmit one or moretransport data blocks using respective MIMO streams over the downlinkchannel in a subsequent TFRE in accordance with the selected MIMO rankas downlink traffic, for example, using a downlink traffic channelHS-PDSCH (High-Speed Physical Downlink Shared Channel). Based onsuccess/failure decoding each received transport data block, wirelessterminal 200 may generate respective HARQ ACK/NACK messages that aretransmitted to base station 100 over the feedback channel.

FIG. 4 is block diagram illustrating elements/functionalities of basestation processor 101 of FIG. 2 supporting two HARQ codeword MIMO with 4channel encoders and up to four rank MIMO downlink transmissionaccording to some embodiments. According to embodiments of FIG. 4, fourchannel encoders CE1, CE2, CE3, and CE4 may be provided for four streamsof transport data blocks B1, B2, B3, and B4, with symbols of one datainput stream for wireless terminal 200 being mapped to as many as fourdifferent data streams. As shown, processor 101 may include transportdata block generator 401, channel encoder 403, modulator 405, layermapper 407, spreader/scrambler 409, and layer precoder 411. Inembodiments of FIG. 4, channel encoder 403 may include channel encodersCE1, CE2, CE3, and CE4 for the four streams of transport data blocks B1,B2, B3, and B4, modulator 405 may include interleavers/modulators IM1,IM2, IM3, and IM4, and layer mapper 407 may be configured to mapresulting symbols of the four streams to as many as four different MIMOlayers (streams) X1, X2, X3, and X4 as discussed in greater detailbelow. Moreover, adaptive controller 415 may be configured to controltransport data block generator 401, channel encoder 403, modulator 405,layer mapper 407, and/or layer precoder 411 responsive to channelquality information (CQI) received as feedback from wireless terminal200. Accordingly, symbols generated responsive to codewords respectivelygenerated by channel encoders CE1, CE2, CE3, and CE4 using differentchannel coding (determined by adaptive controller 415 responsive towireless terminal 200 feedback) may be interleaved and distributed(mapped) to 4 different MIMO layers. More particularly, symbolsgenerated responsive to two data codewords CW (where a data codeword CWis a transport data block with additional channel coding and/or CRCbits) may be interleaved and then split between two different MIMOlayers. According to some embodiments discussed herein, layer mapper 407may perform a one-to-one mapping.

Base station processor 101, for example, may receive input data (e.g.,from core network 70, from another base station, etc.) for transmissionto wireless terminal 200, and transport data block generator 401(including transport data block data generators TB1, TB2, TB3, and TB4)may provide a single stream of data blocks (for rank 1 transmissions) orseparate the input data into a plurality of different streams of datablocks (for rank 2, rank 3, and rank 4 transmission). More particularly,for rank 1 transmissions (providing only 1 MIMO layer/stream), all inputdata may be processed through transport data block generator TB1 toprovide a single stream of transport data blocks B1 (includingindividual transport data blocks B1-1, B1-2, B1-3, etc.) without usingtransport data block generators TB2, TB3, or TB4 and without generatingother streams of transport data blocks B2, B3, or B4. For rank 2transmissions (providing 2 MIMO layers/streams), transport data blockgenerator TB1 may generate a stream of transport data blocks B1(including individual transport data blocks B1-1, B1-2, B1-3, etc.), andtransport data block generator TB3 may generate a stream of transportdata blocks B3 (including individual transport data blocks B3-1, B3-2,B3-3, etc.) without using transport data block generators TB2 or TB4 andwithout generating other streams of transport data blocks B2 or B4. Forrank 3 transmissions (providing 3 MIMO layers/streams), transport datablock generator TB1 may generate a stream of transport data blocks B1(including individual transport data blocks B1-1, B1-2, B1-3, etc.),transport data block generator TB2 may generate a stream of transportdata blocks B2 (including individual transport data blocks B2-1, B2-2,B2-3, etc.), and transport data block generator TB3 may generate astream of transport data blocks B3 (including individual transport datablocks B3-1, B3-2, B3-3, etc.), without using transport data blockgenerator TB4 and without generating another stream of transport datablocks B4. For rank 4 transmissions (providing 4 MIMO layers/streams),transport data block generator TB1 may generate a stream of transportdata blocks B1 (including individual transport data blocks B1-1, B1-2,B1-3, etc.), transport data block generator TB2 may generate a stream oftransport data blocks B2 (including individual transport data blocksB2-1, B2-2, B2-3, etc.), transport data block generator TB3 may generatea stream of transport data blocks B3 (including individual transportdata blocks B3-1, B3-2, B3-3, etc.), and transport data block generatorTB4 may generate a stream of transport data blocks B4 (includingindividual transport data blocks B4-1, B4-2, B4-3, etc.).

Channel encoder 403 (including channel encoders CE1, CE2, CE3, and CE4)may encode the stream/streams of data blocks B1, B2, B3, and/or B4generated by transport data block generator 401 to provide respectivestreams of data codewords CW1 (including individual data codewordscw1-1, cw1-2, cw1-3, etc.), CW2 (including individual data codewordscw2-1, cw2-2, cw2-3, etc.), CW3 (including individual data codewordscw3-1, cw3-2, cw3-3, etc.), and/or CW4 (including individual datacodewords cw4-1, cw4-2, cw4-3, etc.), for example, using turbo coding,convolutional coding, etc. Moreover, coding characteristics (e.g.,coding rates) applied by channel encoders CE1, CE2, CE3, and CE4 may beseparately determined by adaptive controller 415 responsive to wirelessterminal 200 feedback (e.g., CQI regarding the downlink channel). Forrank 1 transmissions, channel encoder 403 may generate a single streamof data codewords CW1 responsive to the stream of data blocks B1 usingonly channel encoder CE1. For rank 2 transmissions, channel encoder 403may generate two streams of data codewords CW1 and CW3 responsive torespective streams of data blocks B1 and B3 using channel encoder CE1and channel encoder CE3. For rank 3 transmissions, channel encoder 403may generate three streams of data codewords CW1, CW2, and CW3responsive to respective streams of data blocks B1, B2, and B3 usingchannel encoder CE1, channel encoder CE2, and channel encoder CE3. Forrank 4 transmissions, channel encoder 403 may generate four streams ofdata codewords CW1, CW2, CW3, and CW4 responsive to respective streamsof data blocks B1, B2, B3, and B4 using channel encoder CE1, channelencoder CE2, channel encoder CE3, and channel encoder CW4. According tosome embodiments, channel encoders CE1, CE2, CE3, and/or CE4 may applydifferent coding characteristics (e.g., different coding rates) duringrank 2, rank 3, and/or rank 4 transmissions to generate respective(differently coded) data codewords cw1-1, cw2-1, cw3-1, and/or cw4-1including data to be transmitted during a same TFRE.

Modulator 405 (including interleaver/modulators IM1, IM2, IM3, and IM4)may interleave and modulate the stream/streams of data codewords CW1,CW2, CW3, and/or CW4 generated by channel encoder 403 to providerespective streams of unmapped symbol blocks D1 (including unmappedsymbol blocks d1-1, d1-2, d1-3, etc.), D2 (including unmapped symbolblocks d2-1, d2-2, d2-3, etc.), D3 (including unmapped symbol blocksd3-1, d3-2, d3-3, etc.), and/or D4 (including unmapped symbol blocksd4-1, d4-2, d4-3, etc.). For rank 1 transmissions (providing only 1 MIMOlayer/stream), modulator 405 may generate a single stream of unmappedsymbol blocks D1 responsive to the stream of data codewords CW1 usingonly interleaver/modulator IM1. For rank 2 transmissions, modulator 405may generate two streams of unmapped symbol blocks D1 and D3 responsiveto respective streams of data codewords CW1 and CW3 usinginterleaver/modulators IM1 and IM3. For rank 3 transmissions, modulator405 may generate three streams of unmapped symbol blocks D1, D2, and D3responsive to respective streams of data codewords CW1, CW2, and CW3using interleaver/modulators IM1, IM2, and IM3. For rank 4transmissions, modulator 405 may generate four streams of unmappedsymbol blocks D1, D2, D3, and D4 responsive to respective streams ofdata codewords CW1, CW2, CW3, and CW4 using interleaver/modulators IM1,IM2, IM3, and IM4. Modulator 405 may apply modulation orders responsiveto input from adaptive controller 415 determined based on CQI feedbackfrom wireless terminal 200.

In addition, each interleaver/modulator IM1, IM2, IM3, and/or IM4 mayinterleave data of two or more codewords of a stream so that two or moreconsecutive unmapped symbol blocks of a respective stream includesymbols representing data of the two or more consecutive codewords. Forexample, data of consecutive data codewords cw1-1 and cw1-2 of codewordstream CW1 may be interleaved and modulated to provide consecutiveunmapped symbol blocks d1-1 and d1-2 of stream D1. Similarly, data ofconsecutive data codewords cw2-1 and cw2-2 of codeword stream CW2 may beinterleaved and modulated to provide consecutive unmapped symbol blocksd2-1 and d2-2 of stream D2; data of consecutive data codewords cw3-1 andcw3-2 of codeword stream CW3 may be interleaved and modulated to provideconsecutive unmapped symbol blocks d3-1 and d3-2 of stream D3; and/ordata of consecutive data codewords cw4-1 and cw4-2 of codeword streamCw4 may be interleaved and modulated to provide consecutive unmappedsymbol blocks d4-1 and d4-2 of stream D4.

Symbols of streams of unmapped symbol blocks D1, D2, D3, and D4 may bemapped to respective streams of mapped symbol blocks X1, X2, X3, and X4(for respective MIMO transmission layers), for example, using aone-to-one mapping. While one-to-one mapping is discussed by way ofexample, other mappings may be used provided that the mapping functionof layer mapper 407 is known to both base station 100 and wirelessterminal 200.

Spreader/scrambler 409 may include four spreader/scramblers SS1, SS2,SS3, and SS4, and for each mapped symbol stream provided by layer mapper407, spreader/scrambler 409 may generate a respective stream of spreadsymbol blocks Y1, Y2, Y3, and Y4 (e.g., using a Walsh code). Layerprecoder 411 may apply a MIMO precoding vector (e.g., by applyingprecoding weights) of the appropriate rank (based on wireless terminalfeedback as interpreted by adaptive controller 415) to the streams ofspread symbol blocks for transmission through transceiver 109 andantennas Ant-1, Ant-2, Ant-3, and Ant-4 of antenna array 117. Accordingto some embodiments, with rank one transmissions, only first layer ofelements (e.g., TB1, CE1, IM1, and/or SS1) of FIG. 4 may be used; withrank two transmissions, two layers of elements (e.g., TB1, TB3, CE1,CE3, IM1, IM3, SS1, and/or SS3) of FIG. 4 may be used; with rank threetransmissions, three layers of elements (e.g., TB1, TB2, TB3, CE1, CE2,CE3, IM1, IM2, IM3, SS1, SS2, and/or SS3) of FIG. 4 may be used; andwith rank four transmissions, four layers of elements (e.g., TB1, TB2,TB3, TB4, CE1, CE2, CE3, CE4, IM1, IM2, IM3, and IM4, SS1, SS2, SS3,and/or SS4) of FIG. 4 may be used. According to some other embodiments,with rank one transmissions, only a first layer of elements (e.g., TB1,CE1, IM1, and/or SS1) of FIG. 4 may be used; with rank twotransmissions, two layers of elements (e.g., TB1, TB2, CE1, CE2, IM1,IM2, SS1, and/or SS2) of FIG. 4 may be used; with rank threetransmissions, three layers of elements (e.g., TB1, TB2, TB3, CE1, CE2,CE3, IM1, IM2, IM3, SS1, SS2, and/or SS3) of FIG. 4 may be used; andwith rank four transmissions, four layers of elements (e.g., TB1, TB2,TB3, TB4, CE1, CE2, CE3, CE4, IM1, IM2, IM3, and IM4, SS1, SS2, SS3,and/or SS4) of FIG. 4 may be used.

In embodiments of FIG. 4, base station processor 101 may support twoHARQ process/codeword MIMO with 4 channel encoders CE1-CE4. Usingfeedback from wireless terminal 200 (indicated by “feedback channel”),adaptive controller 415 chooses transport block length, modulationorder, and coding rate (used by transport block generator 401, encoder403, and/or modulator 405). Adaptive controller 415 also generatesprecoding weight information used by layer precoder 411. Even thoughencoder 403 includes four channel encoders CE1-CE4, wireless terminal200 may only provide feedback information for a maximum of two encodedtransport block codewords. Stated in other words, wireless terminal 200may provide one HARQ process/codeword for rank one transmissions (withone transport data blocks per TFRE using one downlink data streams),wireless terminal 200 may provide two HARQ processes/codewords for ranktwo transmissions (with two transport data blocks per TFRE using twodownlink data streams), wireless terminal 200 may provide two HARQprocesses/codewords for rank three transmissions (with three transportdata blocks per TFRE using three downlink data streams), and wirelessterminal 200 may provide two HARQ processes/codewords for rank fourtransmissions (with four transport data blocks per TFRE using fourdownlink data streams).

For rank three and rank four transmissions, a number of data streamsgenerated by transport block generator 401, encoder 403, modulator 405,and spreader scrambler 409 is greater than a number of HARQprocesses/codewords supported by base station 100 and/or wirelessterminal 200. According to embodiments discussed herein, a HARQprocess/codeword may be mapped to more than one data stream for rank 3and rank 4 transmissions. For rank one transmissions, one HARQprocess/codeword may be mapped directly to a first data stream (e.g.,transmitted using a first transmission layer including TB1, CE1, IM1,and/or SS1 and received using a first reception layer including DM1,SB1, and/or CD1). For rank two transmission, a first HARQprocess/codeword may be mapped directly to a first data stream (e.g.,transmitted using a first transmission layer including TB1, CE1, IM1,and/or SS1 and received using a first reception layer including DM1,SB1, and/or CD1), and a second HARQ process/codeword may be mappeddirectly to a second data stream (e.g., transmitted using a thirdtransmission layer including TB3, CE3, IM3, and/or SS3 and receivedusing a third reception layer including DM3, SB3, and/or CD3). For rankthree transmission, a first HARQ process/codeword may be mapped to afirst data stream (e.g., transmitted using a first transmission layerincluding TB1, CE1, IM1, and/or SS1 and received using a first receptionlayer including DM1, SB1, and/or CD1) and to a second data stream (e.g.,transmitted using a second transmission layer including TB2, CE2, IM2,and/or SS2 and received using a second reception layer including DM2,SB2, and/or CD2), and a second HARQ process/codeword may be mapped to athird data stream (e.g., transmitted using a third transmission layerincluding TB3, CE3, IM3, and/or SS3 and received using a third receptionlayer including DM3, SB3, and/or CD3). For rank four transmission, afirst HARQ process/codeword may be mapped to a first data stream (e.g.,transmitted using a first transmission layer including TB1, CE1, IM1,and/or SS1 and received using a first reception layer including DM1,SB1, and/or CD1) and to a second data stream (e.g., transmitted using asecond transmission layer including TB2, CE2, IM2, and/or SS2 andreceived using a second reception layer including DM2, SB2, and/or CD2), and a second HARQ process/codeword may be mapped to a third datastream (e.g., transmitted using a third transmission layer includingTB3, CE3, IM3, and/or SS3 and received using a third reception layerincluding DM3, SB3, and/or CD3) and to a fourth data stream (e.g.,transmitted using a fourth transmission layer including TB4, CE4, IM4,and/or SS4 and received using a fourth reception layer including DM4,SB4, and/or CD4).

According to some other embodiments, For rank one transmissions, oneHARQ process/codeword may be mapped directly to a first data stream(e.g., transmitted using a first transmission layer including TB1, CE1,IM1, and/or SS1 and received using a first reception layer includingDM1, SB1, and/or CD1). For rank two transmission, a first HARQprocess/codeword may be mapped directly to a first data stream (e.g.,transmitted using a first transmission layer including TB1, CE1, IM1,and/or SS1 and received using a first reception layer including DM1,SB1, and/or CD1), and a second HARQ process/codeword may be mappeddirectly to a second data stream (e.g., transmitted using a thirdtransmission layer including TB2, CE2, IM2, and/or SS2 and receivedusing a third reception layer including DM2, SB2, and/or CD2). For rankthree transmission, a first HARQ process/codeword may be mapped to afirst data stream (e.g., transmitted using a first transmission layerincluding TB1, CE1, IM1, and/or SS1 and received using a first receptionlayer including DM1, SB1, and/or CD1), and a second HARQprocess/codeword may be mapped to a second data stream (e.g.,transmitted using a second transmission layer including TB2, CE2, IM2,and/or SS2 and received using a second reception layer including DM2,SB2, and/or CD2) and to a third data stream (e.g., transmitted using athird transmission layer including TB3, CE3, IM3, and/or SS3 andreceived using a third reception layer including DM3, SB3, and/or CD3).For rank four transmission, a first HARQ process/codeword may be mappedto a first data stream (e.g., transmitted using a first transmissionlayer including TB1, CE1, IM1, and/or SS1 and received using a firstreception layer including DM1, SB1, and/or CD1) and to a fourth datastream (e.g., transmitted using a fourth transmission layer includingTB4, CE4, IM4, and/or SS4 and received using a fourth reception layerincluding DM4, SB4, and/or CD4), and a second HARQ process/codeword maybe mapped to a second data stream (e.g., transmitted using a secondtransmission layer including TB2, CE2, IM2, and/or SS2 and receivedusing a second reception layer including DM2, SB2, and/or CD2) and to athird data stream (e.g., transmitted using a third transmission layerincluding TB3, CE3, IM3, and/or SS3 and received using a third receptionlayer including DM3, SB3, and/or CD3).

Based on the rank chosen by adaptive controller 415, transport datablocks may be passed to encoder 403, and encoder outputs may beinterleaved and modulated using modulator 405. Outputs of modulator 405may be mapped to space time layers using layer mapper 407, and asdiscussed above, layer mapper 407 may provide a one-to-one layermapping. The symbol stream(s) generated by layer mapper 407 may bespread and scrambled using spreader/scrambler 409, and layer precoder411 may precode outputs of spreader/scrambler 409, with precoder outputsbeing passed through transceiver 109 and antenna array 117 (includingAntennas Ant-1, Ant-2, Ant-3, and Ant-4).

At wireless terminal 200, operations of processor 201 may mirroroperations of base station processor 101 when receiving the MIMOdownlink communications transmitted by the base station. Moreparticularly, elements/functionalities of wireless terminal processor201 are illustrated in FIG. 5 mirroring elements/functionalities of basestation processor 101 discussed above with reference to FIG. 4.

Radio signals may be received through MIMO antenna elements of MIMOantenna array 217 and transceiver 209, and the radio signals may bedecoded by layer decoder 601 using a MIMO decoding vector to generate aplurality of MIMO decoded symbol layers X1′, X2′, X3′, and/or X4′depending on MIMO rank used for transmission/reception. Layer Decoder601 may use a decoding vector corresponding to the precoding vector usedby base station 100. Layer decoder 601 may generate a single decodedsymbol layer X1′ for rank 1 reception, layer decoder 601 may generatetwo decoded symbol layers X1′ and X3′ for rank 2 reception, layerdecoder 601 may generate three decoded symbol layers X1′, X2′, and X3′for rank 3 reception, and layer decoder 601 may generate four decodedsymbol layers X1′, X2′, X3′, and X4′ for rank 4 transmission. Layerdecoder 601 may thus perform a converse of operations performed by layerprecoder 411 and spreader/scrambler 409 of base station 100. Layerdecoder 601 may perform functionalities of a MIMO detector(corresponding to a converse of layer precoder 411) and ofdispreading/descrambling blocks for each data stream/layer(corresponding to a converse of spreader/scrambler 409). Layer demapper603 may function as a converse of layer mapper 407 to demap decodedsymbol layers X1′, X2′, X3′, and/or X4′ to respective unmapped symbollayers D1′, D2′, D3′, and/or D4′ according to the transmission rank.

For rank one reception, layer demapper 603 may demap symbols of decodedsymbol layer X1′ blocks x1′-j directly to symbols of unmapped symbollayer D1′ blocks d1′-j, demodulator/deinterleaver DM-1 maydemodulate/deinterleave unmapped symbol layer blocks d1′-j to providedata codewords cw1′-j of codeword stream CW1′, and channel decoder CD1may decode data codewords cw1′-j of codeword stream CW1′ to providetransport blocks B1′-j of stream B1′. Transport block generator 607 maythen pass transport blocks B1′-j of stream B1′ as a data stream. Duringrank one reception, demodulators/deinterleavers DM2, DM3, and DM4 andchannel decoders CD2, CD3, and CD4 may be unused.

For rank two reception, layer decoder 601 may generate decoded symbollayers X1′ and X3′. Layer demapper 603 may demap symbols of decodedsymbol layer X1′ blocks x1′-j directly to symbols of unmapped symbollayer D1′ blocks d1′-j, and layer demapper 603 may demap symbols ofdecoded symbol layer X3′ blocks x3′-j directly to symbols of unmappedsymbol layer D3′ blocks d3′-j. Demodulator/deinterleaver DM-1 maydemodulate/deinterleave unmapped symbol layer blocks d1′-j to providedata codewords cw1′-j of codeword stream CW1′, anddemodulator/deinterleaver DM-3 may demodulate/deinterleave unmappedsymbol layer blocks d3′-j to provide data codewords cw3′-j of codewordstream CW3′. Channel decoder CD1 may decode data codewords cw1′-j ofcodeword stream CW1′ to provide transport blocks B1′-j of stream B1′,and channel decoder CD3 may decode data codewords cw3′-j of codewordstream CW3′ to provide transport blocks B3′-j of stream B3′. Transportblock generator 607 may then combine transport blocks B1′-j and B3′-j ofstreams B1′ and B3′ as a data stream. During rank two reception,demodulators/deinterleavers DM2 and DM4 and channel decoders CD2 and CD4may be unused.

For rank three reception, layer decoder 601 may generate decoded symbollayers X1′, X2′, and X3′. Layer demapper 603 may demap symbols ofdecoded symbol layer X1′ blocks x1′-j directly to symbols of unmappedsymbol layer D1′ blocks d1′-j, layer demapper 603 may demap symbols ofdecoded symbol layer X2′ blocks x2′-j directly to symbols of unmappedsymbol layer D2′ blocks d2′-j, and layer demapper 603 may demap symbolsof decoded symbol layer X3′ blocks x3′-j directly to symbols of unmappedsymbol layer D3′ blocks d3′-j. Demodulator/deinterleaver DM-1 maydemodulate/deinterleave unmapped symbol layer blocks d1′-j to providedata codewords cw1′-j of codeword stream CW1′, demodulator/deinterleaverDM-2 may demodulate/deinterleave unmapped symbol layer blocks d2′-j toprovide data codewords cw2′-j of codeword stream CW2′, anddemodulator/deinterleaver DM-3 may demodulate/deinterleave unmappedsymbol layer blocks d3′-j to provide data codewords cw3′-j of codewordstream CW3′. Channel decoder CD1 may decode data codewords cw1′-j ofcodeword stream CW1′ to provide transport blocks B1′-j of stream B1′,channel decoder CD2 may decode data codewords cw2′-j of codeword streamCW2′ to provide transport blocks B2′-j of stream B2′, and channeldecoder CD3 may decode data codewords cw3′-j of codeword stream CW3′ toprovide transport blocks B3′-j of stream B3′. Transport block generator607 may then combine transport blocks B1′-j, B2′-j, and B3′-j of streamsB1′, B2′, and B3′ as a data stream. During rank three reception,demodulator/deinterleaver DM4 and channel decoder CD4 may be unused.

For rank four reception, layer decoder 601 may generate decoded symbollayers X1′, X2′, X3′, X4′. Layer demapper 603 may demap symbols ofdecoded symbol layer X1′ blocks x1 ′-j directly to symbols of unmappedsymbol layer D1′ blocks d1′-j, layer demapper 603 may demap symbols ofdecoded symbol layer X2′ blocks x2′-j directly to symbols of unmappedsymbol layer D2′ blocks d2′-j, and layer demapper 603 may demap symbolsof decoded symbol layer X3′ blocks x3′-j directly to symbols of unmappedsymbol layer D3′ blocks d3′-j, and layer demapper 603 may demap symbolsof decoded symbol layer X4′ blocks x4′-j directly to symbols of unmappedsymbol layer D4′ blocks d4′-j. Demodulator/deinterleaver DM-1 maydemodulate/deinterleave unmapped symbol layer blocks d1′-j to providedata codewords cw1′-j of codeword stream CW1′, demodulator/deinterleaverDM-2 may demodulate/deinterleave unmapped symbol layer blocks d2′-j toprovide data codewords cw2′-j of codeword stream CW2′,demodulator/deinterleaver DM-3 may demodulate/deinterleave unmappedsymbol layer blocks d3′-j to provide data codewords cw3′-j of codewordstream CW3′, and demodulator/deinterleaver DM-4 maydemodulate/deinterleave unmapped symbol layer blocks d4′-j to providedata codewords cw4′-j of codeword stream CW4′. Channel decoder CD1 maydecode data codewords cw1′-j of codeword stream CW1′ to providetransport blocks B1′-j of stream B1′, channel decoder CD2 may decodedata codewords cw2′-j of codeword stream CW2′ to provide transportblocks B2′-j of stream B2′, channel decoder CD3 may decode datacodewords cw3′-j of codeword stream CW3′ to provide transport blocksB3′-j of stream B3′, and channel decoder CD4 may decode data codewordscw4′-j of codeword stream CW4′ to provide transport blocks B4′-j ofstream B4′. Transport block generator 607 may then combine transportblocks B1′-j, B2′ j, B3′ j, and B4′-j of streams B1′, B2′, B3′, and B4′as a data stream.

As further shown in FIG. 5, a respective soft buffer SB1, SB2, SB3, andSB4 may be provided for each stream of received data, and each decoderCD1, CD2, CD3, and CD4 may be configured to determine whether eachdecoded transport data block passes or fails decoding. In greaterdetail, each undecoded transport data block generated by ademodulator/decoder DM may be saved in the respective soft buffer SBuntil a decoding result is determined by the channel decoder CD. If thetransport data block passes decoding, an ACK (acknowledge message) maybe generated and provided as feedback for the base station, andretransmission of the successfully decoded (passed) data block is notrequired. If the transport data block does not pass decoding, a NACK(negative acknowledge message) may be generated and provided as feedbackfor the base station, and the undecoded output of thedemodulator/deinterleaver (also referred to as soft bits) may be savedin soft buffer SB. Responsive to the NACK, the base station mayretransmit the failed transport data block, and wireless terminal 200may use the retransmitted data block together with the previouslyundecoded output of the demodulator/deinterleaver (that is saved in therespective soft buffer) to decode the retransmitted data block on thesecond pass. By using the soft buffer to combine first and secondversions of the demodulated data block, a likelihood of successfuldecoding may be increased after retransmission.

As shown in FIG. 5, layer decoder 601 (e.g., including a MIMO detectorsuch as a minimum mean squared error or MMSE receiver), may reduceinterference from the multipath channel and/or may reduce other antennainterference. After dispreading, demapping, demodulating, and/ordeinterleaving, wireless terminal 200 may attempt to decode the codedbits of a transport data block using a respective channel decoder. Ifthe decoding attempt fails, wireless terminal 200 buffers the receivedsoft bits of the transport data block in the respective soft buffer, andrequests retransmission of the transport data block by transmitting aNACK message (e.g., as a part of an HARQ-ACK codeword, also referred toas a HARQ codeword). Once the retransmission is received (and subjectedto decoding, demapping, demodulating, and/or deinterleaving) by wirelessterminal 200, wireless terminal may combine the buffered soft bits withthe received soft bits from the retransmission and attempt to decode thecombination using a respective channel decoder.

For soft combining to operate properly, the wireless terminal may needto know whether a received transmission is a new transmission of atransport data block or a retransmission of a previously transmittedtransport data block. For this purpose, the downlink control signalingmay include a data indicator (also referred to as an indicator, a newdata indicator, a new/old data indicator, etc.) that is used by thewireless terminal to control whether the soft buffer should be clearedor whether soft combining of the soft buffer and the received soft bitsshould take place. For a given transmission/retransmission to wirelessterminal 200, the data indicator may thus have one value to indicate aninitial transmission of new data and another value to indicate aretransmission of previously transmitted data.

Whenever a current transmission is not a retransmission, a NodeB basestation MAC-ehs element of base station processor 101 may increment asingle bit data indicator. Accordingly, the single bit data indicatormay be toggled each time a new transport data block is transmitted overa MIMO layer. The data indicator can thus be used by wireless terminalprocessor 201 to clear the soft buffer/buffers for each initialtransmission because no soft combining should be done for new/initialtransmissions. The indicator may also be used to detect error cases inthe status signaling. If the data indicator is not toggled despite thefact that the previous data for the HARQ process in question wascorrectly decoded and acknowledged (using an ACK message), for example,an error in the uplink signaling has most likely occurred. Similarly, ifthe indicator is toggled but the previous data for the HARQ process wasnot correctly decoded, the wireless terminal may replace the datapreviously in the soft buffer for the HARQ process with the new receiveddata.

For rank four transmissions, wireless terminal 200 may thus receive upto four transport data blocks in a same TFRE to support four streams oftransport data blocks. After decoding four data blocks for a TFRE duringa rank 4 transmission, each decoder CD1, CD2, CD3, and CD4 may generatea respective local ACK or NACK depending on whether the respectivetransport data block passed or failed decoding. In a rank 4transmission, decoders CD1 and CD2 may be mapped to the first HARQprocess so that the resulting HARQ ACK/NACK is an ACK only if bothdecoders CD1 and CD2 generate a local ACK and the resulting HARQAKC/NACK message from the first HARQ process is a NACK if either decoderCD1 or CD2 generated a local NACK; and decoders CD3 and CD4 may bemapped to the second HARQ process so that the resulting HARQ ACK/NACKfrom the second HARQ process is an ACK only if both decoders CD3 and CD4generate a local ACK and the resulting HARQ AKC/NACK message is a NACKif either decoder CD3 or CD4 generated a local NACK.

For rank three transmissions, wireless terminal 200 may thus receive upto three transport data blocks in a same TFRE. After decoding three datablocks for a TFRE during a rank 3 transmission, each decoder CD1, CD2,and CD3 may generate a respective local ACK or NACK depending on whetherthe respective transport data block passed or failed decoding. In a rank3 transmission, decoders CD1 and CD2 may be mapped to the first HARQprocess so that the resulting HARQ ACK/NACK is an ACK only if bothdecoders CD1 and CD2 generate a local ACK and the resulting HARQAKC/NACK message from the first HARQ process is a NACK if either decoderCD1 or CD2 generated a local NACK; and decoder CD3 may be mapped to thesecond HARQ process so that the resulting HARQ ACK/NACK from the secondHARQ process is an ACK if decoder CD3 generates a local ACK and theresulting HARQ AKC/NACK message is a NACK if decoder CD3 generates alocal NACK.

For rank two transmissions, wireless terminal 200 may receive up to twotransport data blocks in a same TFRE. After decoding two data blocks fora TFRE during a rank 2 transmission, each decoder CD1 and CD3 maygenerate a respective local ACK or NACK depending on whether therespective transport data block passed or failed decoding. In a rank twotransmission, decoders CD1 may be mapped to the first HARQ process sothat the resulting HARQ ACK/NACK is an ACK only if decoder CD1 generatesa local ACK and the resulting HARQ AKC/NACK message from the first HARQprocess is a NACK if decoder CD1 generates a local NACK; and decoder CD3may be mapped to the second HARQ process so that the resulting HARQACK/NACK from the second HARQ process is an ACK if decoder CD3 generatesa local ACK and the resulting HARQ AKC/NACK message is a NACK if decoderCD3 generates a local NACK.

For rank one transmissions, wireless terminal 200 may thus receive onetransport data block in a TFRE. After decoding one data block for a TFREduring a rank 1 transmission, decoder CD1 may generate a respective ACKor NACK depending on whether the transport data block passed or faileddecoding. In a rank one transmission, decoder CD1 may be mapped to thefirst HARQ process so that the resulting HARQ ACK/NACK is an ACK ifdecoder CD1 generates a local ACK and the resulting HARQ AKC/NACKmessage from the first HARQ process is a NACK if decoder CD1 generates alocal NACK.

According to some other embodiments, first transmission/reception layersTL1/RL1 may be used during rank 1 transmission/reception, and HARQprocess HARQ-1 may be mapped to a data block of the firsttransmission/reception layers TL1/RL1 during rank 1transmission/reception. First and second transmission/reception layersTL1/RL1 and TL2/RL2 may be used during rank 2 transmission/reception,HARQ process HARQ-1 may be mapped to a data block of the firsttransmission/reception layers TL1/RL1 during rank 1transmission/reception, and HARQ process HARQ-2 may be mapped to a datablock of the second transmission/reception layers TL2/RL2 during rank 2transmission/reception. First, second, and third transmission/receptionlayers TL1/RL1, TL2/RL2, and TL3/RL3 may be used during rank 3transmission/reception, HARQ process HARQ-1 may be mapped to a datablock of the first transmission/reception layers TL1/RL1 during rank 3transmission/reception, and HARQ process HARQ-2 may be mapped to datablocks of the second and third transmission/reception layers TL2/RL2 andTL3/RL3 during rank 3 transmission/reception. First, second, third, andfourth transmission/reception layers TL1/RL1, TL2/RL2, TL3/RL3, andTL4/RL4 may be used during rank 4 transmission/reception, HARQ processHARQ-1 may be mapped to data blocks of the first and fourthtransmission/reception layers TL1/RL1 and TL4/RL4 during rank 4transmission/reception, and HARQ process HARQ-2 may be mapped to datablocks of the second and third transmission/reception layers TL2/RL2 andTL3/RL3 during rank 4 transmission/reception. A MIMO layer (supported byrespective transmission/reception layers) may thus define a logicalchannel over which a data block (or a stream of data blocks) istransmitted.

According to embodiments discussed herein, a HARQ process in a MAC-ehsof wireless terminal processor 101 may provide MAC functionalityillustrated in FIG. 6. FIG. 6 illustrates MAC (Media Access Control)functionality at wireless terminal 200. As shown in FIG. 6, one HARQentity may handle HARQ functionality for one user per HS-DSCH (HighSpeed Downlink Shared Channel). One HARQ entity may be capable ofsupporting multiple instances (multiple HARQ processes) of stop and waitHARQ protocols. According to some embodiments, there shall be one HARQentity per HS-DSCH, one HARQ process per TTI (Transmission TimeInterval) for single stream (rank one) transmission, and two HARQprocesses per TTI for two stream (rank two) transmission, three stream(rank three) transmission, and four stream (rank four) transmission.

Because only 2 HARQ processes are supported for MIMOtransmission/reception using three downlink streams (rank three) and forMIMO transmission/reception using four downlink stream (rank four), themapping of soft buffers may be provided according to the table of FIG.7A for rank 3 and according to the table of FIG. 7B rank 4 downlinktransmission/reception. Note that any one of the combinations of FIG. 7Amay be used for rank 4 downlink transmission, and that any one of thecombinations of FIG. 7B may be used for rank 3 down link transmissions.Whenever the data indicator for a shared HARQ process (i.e., a HARQprocess shared by two or more streams/layers) indicates that new datahas been initially transmitted over the downlink (e.g., the dataindicator has been toggled), the soft buffers for both/all streamsassociated with the shared HARQ process should be cleared. Whenever thedata indicator for a shared HARQ process (i.e., a HARQ process shared bytwo or more streams/layers) indicates that old data is beingretransmitted, the soft buffers for both/all streams associated with theshared HARQ process should be combined with the retransmitted data ofthe respective data streams.

For rank one transmissions, a first HARQ process may be used for thesingle downlink data stream (e.g., for a downlink stream transmittedusing TB1, CE1, IM1, and/or SS1 defining a first transmission layer andreceived using DM1, SB1, and/or CD1 defining a first reception layer).Accordingly, one data indicator flag may be transmitted by base stationfor one transport data block of the downlink data stream, and wirelessterminal 200 may receive the one transport data block using DM1, SB1,and CD1. If the data indicator indicates that the transport data blockis a new/initial transmission, wireless terminal 200 may clear softbuffer SB1 and attempt to decode using channel decoder CD1. If the dataindicator indicates that the transport data block is a retransmission ofa previously failed transmission, wireless terminal 200 may combine softbits of the retransmission (generated by demodulator/deinterleaver DM1)with soft bits from soft buffer SB1 and attempt to decode thecombination using channel decoder CD1. If channel decoder CD1 is able tosuccessfully decode the transmission/retransmission, an ACK message isgenerated and transmitted to base station 100 (e.g., as an element of aHARQ-ACK codeword, also referred to as a HARQ codeword). If channeldecoder CD1 is unable to decode the transmission/retransmission, a NACKmessage is generated and transmitted to base station 100 (e.g., as anelement of a HARQ-ACK codeword, also referred to as a HARQ codeword). Asingle HARQ process (including a data indicator, a NACK message and/oran ACK message) may thus map to each transport data block transmittedover the rank/layer one downlink data stream.

For rank two transmissions, a first HARQ process (including a dataindicator, a NACK message and/or an ACK message) may map to eachtransport data block transmitted over a first stream of the rank twotransmission (e.g., for a downlink stream transmitted using TB1, CE1,IM1, and/or SS1 defining a first transmission layer and received usingDM1, SB1, and/or CD1 defining a first reception layer), and a secondHARQ process (including a data indicator, a NACK message and/or an ACKmessage) may map to each transport data block transmitted over a secondstream of the rank two transmission (e.g., for a downlink streamtransmitted using TB3, CE3, IM3, and/or SS3 defining a thirdtransmission layer and received using DM3, SB3, and/or CD3 defining athird reception layer). Each of the first and second HARQ processes maythus operate for transport data blocks of respective streams of the ranktwo transmissions as discussed above with respect to rank/layer onetransmissions. Stated in other words, a respective data indicator may beprovided for each transport data block received during a same TFRE, softbuffers for the respective downlink data streams may be independentlycleared or maintained for retransmission combining responsive to therespective data indicators, and respective ACK/NACK messages may begenerated and transmitted to base station 100 for each transport datablock received during a same TFRE.

For higher order transmission ranks/layers, however, a HARQ process maybe shared by two or more downlink data streams to reduce uplink feedbacksignaling. For rank three downlink transmissions, a first HARQ process(including one data indicator and one ACK/NACK message per TFRE) may mapto first and second streams of transport data blocks, and a second HARQprocess (including one data indicator and one ACK/NACK message per TFRE)may map to a third stream of transport data blocks. For rank threedownlink transmissions, for example, a first HARQ process may map toeach transport data block transmitted over a first stream of the rankthree transmission (e.g., for a downlink stream transmitted using TB1,CE1, IM1, and/or SS1 defining a first transmission layer and receivedusing DM1, SB1, and/or CD1 defining a first reception layer) and to eachtransport data block transmitted over a second stream of the rank threetransmission (e.g., for a downlink stream transmitted using TB2, CE2,IM2, and/or SS2 defining a second transmission layer and received usingDM2, SB2, and/or CD2 defining a second reception layer); and a secondHARQ process may map to each transport data block transmitted over athird stream of the rank three transmission (e.g., for a downlink streamtransmitted using TB3, CE3, IM3, and/or SS3 defining a thirdtransmission layer and received using DM3, SB3, and/or CD3 defining athird reception layer). During rank three transmissions, the first HARQprocess may thus be shared by data blocks of the first and secondstreams that are transmitted using a same TFRE so that the first andsecond streams are bundled to a same HARQ process. Accordingly, one HARQACK/NACK message and one data indicator may be mapped to both datablocks of a same TFRE for the first and second streams during rank threetransmission. In contrast, the second HARQ process, may be applied toonly the third data stream, so that one HARQ ANK/NACK message and onedata indicator may be mapped to one data block of each TFRE of the thirdstream.

Accordingly, first, second, and third transport data blocks may betransmitted during a same TFRE over respective the first, second, andthird streams during a rank three transmission. A first data indicatormay be transmitted by base station 100 for both of the first and secondtransport data blocks of the first and second downlink data streams. Ifthe first data indicator indicates a new/initial transmission, wirelessterminal 200 may clear soft buffers SB1 and SB2 and attempt to decodethe first and second transport data blocks using channel decoders CD1and CD2. If the first data indicator indicates a retransmission,wireless terminal 200 may combine soft bits of the first and secondtransport data blocks (generated by demodulators/deinterleavers DM1 andDM2) with soft bits from respective soft buffers SB1 and SB2 and attemptto decode the combinations using respective channel decoders CD1 andCD2. If both channel decoders CD1 and CD2 are able to successfullydecode the transmissions/retransmissions, an ACK message is generatedand transmitted to base station 100 (e.g., as an element of a sharedHARQ-ACK codeword, also referred to as a HARQ codeword). If either ofchannel decoders CD1 or CD2 is unable to decode thetransmissions/retransmissions, a NACK message is generated andtransmitted to base station 100 (e.g., as an element of a sharedHARQ-ACK codeword, also referred to as a HARQ codeword). The first HARQprocess (including a single data indicator and a single ACK/NACKmessage) may thus be shared by two transport data blocks transmittedover different downlink data streams during a same TFRE. A second dataindicator may be transmitted by base station 100 for the third transportdata block of the third stream, and soft buffer SB3 may be cleared ifthe second data indicator indicates that the third transport data blockis an initial transmission, or soft buffer SB3 may be maintained forcombined decoding if the second data indicator indicates that the firsttransport data block is a retransmission. If channel decoder CD3 is ableto successfully decode the transmission/retransmission, an ACK messageis generated and transmitted to base station 100 (e.g., as an element ofa HARQ-ACK codeword, also referred to as a HARQ codeword). If channeldecoder CD3 is unable to decode the transmissions/retransmissions, aNACK message is generated and transmitted to base station 100 (e.g., asan element of a HARQ-ACK codeword, also referred to as a HARQ codeword).

For rank/layer four downlink transmissions according to someembodiments, the first HARQ process may be shared between a first stream(e.g., for a downlink stream transmitted using TB1, CE1, IM1, and/or SS1defining a first transmission layer and received using DM1, SB1, and/orCD1 defining a first reception layer) and a second stream (e.g., for adownlink stream transmitted using TB2, CE2, IM2, and/or SS2 defining asecond transmission layer and received using DM2, SB2, and/or CD2defining a second reception layer), and the second HARQ process may beshared between a third stream (e.g., for a downlink stream transmittedusing TB3, CE3, IM3, and/or SS3 defining a third transmission layer andreceived using DM3, SB3, and/or CD3 defining a third reception layer)and a fourth stream (e.g., for a downlink stream transmitted using TB4,CE4, IM4, and/or SS4 defining a fourth transmission layer and receivedusing DM4, SB4, and/or CD4 defining a fourth reception layer). Thesharing of a HARQ process between any two data streams may be the sameas discussed above with respect the sharing of the first HARQ processbetween first and second data streams during rank three transmissions.Where a HARQ process is shared between two streams, the HARQ processprovides one data indicator and one ACK/NACK message for each TFRE forall data streams sharing the HARQ process.

A HARQ process/identification (e.g., HARQ-1/H_a or HARQ-2/H_b) may thusbe used to support downlink transmissions/retransmissions from basestation 100 to wireless terminal 200, and two HARQprocesses/identifications may support HARQ ACK/NACK/DTX signaling for4-antenna MIMO systems supporting up to 4 layer/stream downlinktransmissions (and/or higher antenna systems supporting higherrank/layer transmissions). For rank 1 transmissions, first HARQprocess/identification HARQ-1/H_a maps to a first layer supported bytransmission/reception layers TL1/RL1. For rank 2 transmissions, firstHARQ process/identification HARQ-1/H_a maps to the first layer supportedby transmission/reception layers TL1/RL1, and second HARQprocess/identification HARQ-2/H_a maps to a second layer supported bytransmission/reception layers TL2/RL2. For rank 3 transmissions, firstHARQ process/identification HARQ-1/H_a maps to the first layer supportedby transmission/reception layers TL1/RL1, and second HARQprocess/identification HARQ-2/H_b maps to second and third layerssupported by transmission/reception layers TL2/RL2 and TL3/RL3. For rank4 transmissions, first HARQ process/identification HARQ-1/H_a maps tofirst and fourth layers supported by transmission/reception layersTL1/RL1 and TL4/RL4, and second HARQ process/identification HARQ-2/H_bmaps to second and third layers supported by transmission/receptionlayers TL2/RL2 and TL3/RL3.

Because of the delay between base station 100 transmitting a first datablock(s) to wireless terminal 200 during a first downlink TTI/TFRE andreceiving a HARQ ACK/NACK response(s) for the first data block(s) fromwireless terminal 200, second data block(s) may be transmitted towireless terminal 200 during a second downlink TTI/TFRE before receivingthe HARQ ACK/NACK response(s) for the first data block(s). Accordingly,HARQ process identifications may be used by base station 100 todistinguish between different HARQ ACK/NACK responses for different datablocks of different downlink TTIs/TFREs transmitted to the same wirelessterminal 200. Stated in other words, HARQ process identifications may beused to match HARQ ACK/NACK responses with the appropriate data block(s)and TTI/TFRE. HARQ process identifications may also be used by wirelessterminal 100 to match the data block/blocks with the appropriate softbits from the respective soft buffer/buffers.

A same HARQ process identification may thus be used for the initialtransmission and each retransmission of a data block/blocks to wirelessterminal 200 until either the data block/blocks is/are successfullyreceived/decoded by wireless terminal 200 (as indicated by an ACK) oruntil a maximum allowed number of retransmissions have occurred. Oncethe data block/blocks have been successfully received/decoded or amaximum number of retransmissions has occurred, the HARQ processidentification for the data block/blocks may be destroyed, meaning thatthe HARQ process identification may then be reused for a new datablock/blocks.

According to some embodiments, a HARQ process identification may beselected from one of eight values (e.g., 1, 2, 3, 3, 5, 6, 7, or 8). Forrank 1, 2, and 3 downlink transmissions to wireless terminal 200, HARQprocess identification H_a is mapped to a first HARQ process HARQ-1 forlayer 1 transmission using transmission/reception layers TL1/RL1. Forrank 4 downlink transmissions to wireless terminal, HARQ processidentification H_a is mapped to the first HARQ process HARQ-1 for layer1 and 4 transmissions using transmission/reception layers TL1/RL1 andTL4/RL4. For rank 2 downlink transmissions to wireless terminal 200,HARQ process identification H_b is mapped to a second HARQ processHARQ-2 for layer 2 transmission using transmission/reception layerTL2/RL2. For rank 3 and 4 downlink transmissions to wireless terminal,HARQ process identification H_b is mapped to the second HARQ processHARQ-2 for layer 2 and 3 transmissions using transmission/receptionlayers TL2/RL2 and TL3/RL3. Accordingly, HARQ process HARQ-1 andidentification H_a are used for rank 1, 2, 3, and 4 transmissions, andHARQ process HARQ-2 and identification H_b are used for rank 2, 3, and 4transmissions.

For an initial rank 1 transmission of a data block, a currently unusedidentification value (e.g., selected from 1-8) is assigned to H_a forHARQ process HARQ-1, and H_a is used to identify the instance of HARQ-1that is applied to transmissions/retransmissions of the layer 1 datablock and that is applied to HARQ ACK/NACK responses corresponding tothe layer 1 data block.

For an initial rank 2, 3, or 4 transmission of data blocks using bothHARQ processes HARQ-1 and HARQ-2 during a same TTI/TFRE, a currentlyunused identification value (e.g., selected from 1-8) is assigned to H_afor HARQ process HARQ-1, and another identification value is assigned toH_b for process HARQ-2 (e.g., as a function of H_a). Accordingly, H_a isused to identify the instance of HARQ-1 that is applied totransmissions/retransmissions of layer 1/4 data block/blocks (for layer1 and/or 4 transmissions/retransmissions) and that is applied to HARQACK/NACK responses corresponding to the layer 1/4 data blocks, and H_bis used to identify the instance of HARQ-2 that is applied totransmissions/retransmissions of the layer 2/3 data block/blocks (forlayer 2 and/or 3 transmissions/retransmissions) and that is applied toHARQ ACK/NACK responses corresponding to the layer 2/3 datablock/blocks.

According to some embodiments, HARQ process identification H_b may beassigned as a function of HARQ process identification H_a. With eightdifferent HARQ process identification values from one to eight, forexample, identification H_b may be assigned according to the followingformula:H_b=(H_a+N/2)mod(N),where N is the number of HARQ processes (e.g., two for HARQ-1 andHARQ-2) as configured by higher layers and/or by the radio networkcontroller. With two HARQ processes and eight different HARQ processidentification values, identification H_b may be selected as a functionof H_a according to the following table:

H_a H_b 1 5 2 6 3 7 4 8 5 1 6 2 7 3 8 4Accordingly, only one of the HARQ process identifications (e.g., H_a)may need to be transmitted between base station 100 and wirelessterminal 200, with the other HARQ process identification (e.g., H_b)being derived at the receiving device using H_a.

If the Node B (base station) schedules three transport blocks in anytransmission (i.e., rank 3), for retransmissions, the second transportblock and the third transport block are retransmitted with the same HARQprocess identifier (that was shared by the second and third transportblocks for the initial transmission) as discussed above. If the Node Bschedules four transport blocks in any transmission, forretransmissions, the primary transport block and the fourth transportblock are re-transmitted with the same HARQ process identifier (that wasshared by the primary and fourth transport blocks for the initialtransmission), and the second and third transport blocks arere-transmitted with the same HARQ process identifier (that was shared bythe second and third transport blocks for the initial transmission), asdiscussed above.

Operations of a HARQ process shared by multiple data streams will now bediscussed in greater detail below with respect to the flow charts ofFIGS. 8A and 8B. FIG. 8A illustrates operations of a base stationtransmitting multiple MIMO data streams using a shared HARQ processaccording to some embodiments, and FIG. 8B illustrates operations of awireless terminal receiving multiple MIMO data streams using a sharedHARQ process according to some embodiments. Operations of FIGS. 8A and8B may be discussed concurrently because the base station and wirelessterminal operations may be interleaved.

As shown in FIG. 8A, base station processor 101 may determine for anHARQ process if the HARQ process is being applied to a single MIMO datastream or if the HARQ process is being shared by multiple (e.g., two)MIMO data streams at block 811. If the HARQ process is being applied toonly one MIMO data stream, the HARQ process may be applied individuallyto the single MIMO data stream at block 815 so that one ACK/NACK message(received from wireless terminal 200) from the prior TFRE is appliedonly to the single MIMO data stream for the current TFRE, and so thatone data indicator is applied only to the single MIMO data stream forthe current TFRE.

If the HARQ process is being shared by multiple MIMO data streams atblock 811, base station processor 101, may determine whether an ACKmessage or a NACK message was received in response to transport datablocks transmitted over the multiple MIMO data streams in a/thepreceding TFRE. As discussed above, one ACK or NACK message may betransmitted by wireless terminal 200 for a plurality data streamssharing a HARQ process.

If an ACK message was received for the prior TFRE transmission at block817, base station processor 101 may generate and transmit a dataindicator indicating an initial transmission of new data for alltransport data blocks being transmitted during the current TFRE for thedata streams sharing the HARQ process at block 819. At block 821, basestation processor 101 may generate and transmit new transport datablocks for all data streams sharing the HARQ process.

If a NACK message was received for the prior TFRE transmission at block817, base station processor 101 may generate and transmit a dataindicator indicating a retransmission of the prior data for alltransport data blocks being transmitted during the current TFRE for thedata streams sharing the HARQ process at block 831. At block 833, basestation processor 101 may retransmit the previously transmittedtransport data blocks for all data streams sharing the HARQ process. Asingle NACK message may thus result in retransmission of transport datablocks for all data streams sharing the HARQ process.

As shown in FIG. 8B, responsive to receiving data for a TFRE at block849, wireless terminal processor 201 may determine for a HARQ process ifthe HARQ process is being applied to a single MIMO data stream or if theHARQ process is being shared by multiple (e.g., two) MIMO data streamsat block 851. If the HARQ process is being applied to only one MIMO datastream, the HARQ process may be applied individually to the single MIMOdata stream at block 853 so that one ACK/NACK message is generated foronly the single MIMO data stream, and so that a data indicator isapplied only to the single MIMO data stream for the current TFRE. Asdiscussed above with respect to a four antenna system, for example, afirst HARQ process (HARQ-1) may be applied individually to a first MIMOdata stream (e.g., using TB1, CE1, IM1, DM1, SB1, and/or CD1) for rank1, rank 2, and rank 3 transmission/reception, and a second HARQ process(HARQ-2) may be applied individually to a second MIMO data stream (e.g.,using TB2, CE2, IM2, DM2, SB2, and/or CD2) for rank 2transmission/reception.

If the HARQ process is being shared by multiple MIMO data streams atblock 851, wireless terminal processor 201 may determine at block 855whether a data indicator (transmitted by base station 100) indicatesthat the transport data blocks are initial transmissions of new data orretransmissions of old data transmitted in a previous TFRE.

As discussed above with respect to a four antenna system, for example, afirst HARQ process (HARQ-1) may be shared by a first MIMO data stream(e.g., using TB1, CE1, IM1, DM1, SB1, and/or CD1) and a fourth MIMO datastream (e.g., using TB4, CE4, IM 4, DM4, SB4, and/or CD4) for rank 4transmission/reception, and a second HARQ process (HARQ-2) may be sharedby a second MIMO data stream (e.g., using TB2, CE2, IM2, DM2, SB2,and/or CD2) and a third MIMO data stream (e.g., using TB3, CE3, IM3,DM3, SB3, and/or CD3) for rank 3 and rank 4 transmission/reception.

If the transport data blocks of the shared HARQ process are initialtransmissions of new data, all soft buffers of the data streams sharingthe HAQ process are cleared at block 861 (responsive to the one dataindicator), and each of the transport data blocks of the data streamssharing the HARQ process are separately demodulated at block 863 togenerate soft bits for the respective transport data blocks. The softbits for the respective transport data blocks are then decoded at bock865 to generate the original transport data blocks. If all of thecurrent transport data blocks (of the current TFRE) of the MIMO datastreams sharing the HARQ process are successfully decoded at block 867,one ACK message may be generated and transmitted to base station 100 atblock 869 for all of the transport data blocks sharing the HARQ process.If one of the current transport data blocks (of the current TFRE) of theMIMO data streams sharing the HARQ process fails decoding at block 867,one NACK message may be generated and transmitted to base station 100 atblock 871 for all of the transport data blocks sharing the HARQ process.

If the transport data blocks of the shared HARQ process areretransmissions at block 855, all soft buffers of the data streamssharing the HAQ process are maintained at block 881 (responsive to theone data indicator indicating retransmission), and each of the transportdata blocks of the data streams sharing the HARQ process are separatelydemodulated at block 883 to generate soft bits for the respectivetransport data blocks. The soft bits for the respective transport datablocks are then combined with the corresponding soft bits fromrespective soft buffers at block 885, and the combinations of old/newsoft bits are separately decoded at bock 887 to generate the originaltransport data blocks. If all of the current transport data blocks (ofthe current TFRE) of the MIMO data streams sharing the HARQ process aresuccessfully decoded at block 887 and 867, one ACK message may begenerated and transmitted to base station 100 at block 869 for all ofthe transport data blocks sharing the HARQ process. If one of thecurrent transport data blocks (of the current TFRE) of the MIMO datastreams sharing the HARQ process fails decoding at block 867, one NACKmessage may be generated and transmitted to base station 100 at block871 for all of the transport data blocks sharing the HARQ process.

In a multiple HARQ codeword MIMO system supporting up to four MIMO datastreams with HARQ codeword dimensioning, for example, two HARQ codewordsmay be mapped to three MIMO data streams/layers for rank 3 transmissionsand to four MIMO data streams/layers for rank 4 transmissions. For rankthree downlink transmissions, for example, a first HARQ process (HARQ-1)may map to each transport data block transmitted over a first stream ofthe rank three transmission (e.g., for a downlink stream transmittedusing TB1, CE1, IM1, and/or SS1 defining a first transmission layer TL1and received using DM1, SB1, and/or CD1 defining a first reception layerRL1) and to each transport data block transmitted over a second streamof the rank three transmission (e.g., for a downlink stream transmittedusing TB2, CE2, IM2, and/or SS2 defining a second transmission layer TL2and received using DM2, SB2, and/or CD2 defining a second receptionlayer RL2); and a second HARQ process (HARQ-2) may map to each transportdata block transmitted over a third stream of the rank threetransmission (e.g., for a downlink stream transmitted using TB3, CE3,IM3, and/or SS3 defining a third transmission layer TL3 and receivedusing DM3, SB3, and/or CD3 defining a third reception layer RL3). Forrank four downlink transmissions, the first HARQ process (HARQ-1) maymap to each transport data block transmitted over a first stream of therank four transmission (e.g., for a downlink stream transmitted usingTB1, CE1, IM1, and/or SS1 defining a first transmission layer TL1 andreceived using DM1, SB1, and/or CD1 defining a first reception layerRL4) and to each transport data block transmitted over a second streamof the rank four transmission (e.g., for a downlink stream transmittedusing TB2, CE2, IM2, and/or SS2 defining a second transmission layer TL2and received using DM2, SB2, and/or CD2 defining a second receptionlayer RL2); and the second HARQ process (HARQ-2) may map to eachtransport data block transmitted over a third stream of the rank fourtransmission (e.g., for a downlink stream transmitted using TB3, CE3,IM3, and/or SS3 defining a third transmission layer TL3 and receivedusing DM3, SB3, and/or CD3 defining a third reception layer TL4) andover a fourth stream of the rank four transmission (e.g., for a downlinkstream transmitted using TB4, CE4, IM4, and/or SS4 defining a fourthtransmission layer TL4 and received using DM4, SB4, and/or CD4 defininga fourth reception layer RL4). This sharing of HARQ processes may bereferred to as bundling and/or sharing.

As further discussed above, if either data block sharing a HARQ processis not successfully decoded at the respective channel decoder (e.g., ifa data block fails at either of channel decoders CD1 or CD2 sharing thefirst HARQ process (HARQ-1) during a rank 3 or a rank 4 transmission, orif a data block fails at either of channel decoders CD3 or CD4 sharingthe second HARQ process (HARQ-2) during a rank 4 transmission, a singleNACK for the bundled/shared HARQ process may be transmitted to basestation 100 and soft bits for both of the failed data blocks may besaved at respective soft buffers (corresponding to the respectivechannel decoders and/or HARQ processes) for subsequent combining withretransmissions of the failed data blocks. If the transmission rankrequested by wireless terminal 200 changes between transmitting theinitial data blocks and retransmitting the failed data blocks, however,the retransmission may be complicated if the updated rank does notsupport the shared HARQ process for the failed data blocks. Moreparticularly, the soft buffers may be mapped to respective HARQprocesses so that the soft bits saved in one or both of the respectivesoft buffers may be unavailable if the mapping of the bundled HARQprocess according to the updated transmission rank does not include bothsoft buffers. Accordingly, base station 100 may be unable to retransmitthe failed bundled data blocks using the updated rank thereby increasingdelay in retransmitting the failed bundled data blocks.

In a rank 3 or a rank 4 transmission using one TFRE to transmit three orfour data blocks, for example, a first data block may be transmittedusing a first transmission layer TL1 (e.g., including TB1, CE1, IM1,and/or SS1) and received using a first reception layer RL1 (e.g.,including DM1, SB1, and/or CD1), and a second data block may betransmitted using a second transmission layer TL2 (e.g., including TB2,CE2, IM2, and/or SS2) and received using a second reception layer RL2(e.g., including DM2, SB2, and/or CD2). If either or both of the firstor second data blocks fails decoding at respective channel decoder CD1and/or CD2, wireless terminal 200 may transmit a single NACK message tobase station 100 indicating failure of the bundled first and second datapackets, and soft bits of the first and second data blocks (fromrespective demodulators/deinterleavers DM1 and DM2) may be saved atrespective soft buffers SB1 and SB2 for subsequent combining withretransmissions of the first and second data blocks. If the transmissionrank is reduced to rank 1 or rank 2, however, transmission/receptionalong the second transmission layer TL2 (e.g., including TB2, CE2, IM2,and/or SS2) and the second reception layer RL2 (e.g., including DM2,SB2, and/or CD2) may no longer be supported so that parallelretransmission of the first and second data packets using the first HARQprocess HARQ-1 (including both soft buffers SB1 and SB2) may not bepossible.

Similarly, in a rank 4 transmission using one TFRE, for example, a thirddata block may be transmitted using a third transmission layer TL3(e.g., including TB3, CE3, IM3, and/or SS3) and received using a thirdreception layer RL3 (e.g., including DM3, SB3, and/or CD3), and a fourthdata block may be transmitted using a fourth transmission layer TL4(e.g., including TB4, CE4, IM4, and/or SS4) and received using a fourthreception layer RL4 (e.g., including DM4, SB4, and/or CD4). If either orboth of the third and/or fourth data blocks fails decoding at respectivechannel decoder CD3 and/or CD4, wireless terminal 200 may transmit asingle NACK message to base station 100 indicating failure of thebundled third and fourth data blocks, and soft bits of the third andfourth data blocks (from respective demodulators/deinterleavers DM3 andDM4) may be saved at respective soft buffers SB3 and SB4 for subsequentcombining with retransmissions of the first and second data blocks. Ifthe transmission rank is reduced to rank 1, rank 2, or rank 3, however,transmission/reception along the third and/or fourthtransmission/reception layers may no longer be supported so thatparallel retransmission of the third and fourth data packets using thesecond HARQ process HARQ-2 (including both soft buffers SB3 and SB4) maynot be possible.

According to some embodiments, base station 100 may delay changing adownlink transmission rank for wireless terminal 200 until either ACKshave been received for all data blocks previously transmitted towireless terminal 200 or a maximum number of retransmissions haveoccurred. Accordingly, mappings of HARQ processes totransmission/reception layers (including respective soft buffers) may bemaintained as needed for retransmissions of any failed data blocks thatwere initially transmitted using a shared/bundled HARQ process. Becausedownlink channel conditions may vary at a relatively low rate over twoto three consecutive transmission time intervals, however, a relativelylow transmission quality of the downlink channel which resulted in theinitial channel decoder failure may remain relatively low so that ahigher number of retransmissions may be needed to achieve successfuldecoding and CRC validation of the failed data block(s). The increasednumber of retransmissions, however, may increase delay transferring thedata block(s) to higher processing layers, and/or an increased residualblock error rate may occur.

According to some embodiments, base station processor 101 may usemapping tables of FIGS. 10-13 to retransmit failed data packets (e.g.,associated with a bundled HARQ process) when wireless terminal 200reports/requests a downlink transmission rank that is different than thedownlink transmission rank used to initially transmit the now faileddata packets. Some embodiments are discussed in greater detail belowwith respect to the tables of FIGS. 9-13 for systems including 4transmit and 4 receive MIMO antennas supporting one, two, three, andfour MIMO transmission ranks. While embodiments relating to 4 transmitand 4 receive MIMO antennas are discussed by way of example, embodimentsmay be applied to systems including fewer and/or more MIMO transmit andreceive antennas.

According to some embodiments, base station processor 101 may operateaccording to a retransmission algorithm such that if a NACK is generatedfor a bundled HARQ ACK/NACK message for a plurality of data blocks(e.g., for first and second data blocks of a same TFREtransmitted/received using first and second transmission/receptionlayers including channel decoders CD1 and CD2 during rank 3 and/or rank4 transmissions, and/or transmitted/received using third and fourthtransmission/reception layers including channel decoders CD3 and CD 4during rank 4 transmissions), the bundled data blocks may beretransmitted using a rank selected to maintain a HARQ process mappingfor the bundled HARQ NACK message. For example, a base station processor101 may maintain a rank that is at least as high as that used for theoriginal transmission even if wireless terminal 200 hasrequested/recommended a lower rank. According to some embodiments, basestation processor 101 may maintain a same transmission rank forretransmission of bundled data packets even if wireless terminal 200 hasrequested/recommended a lower downlink transmission rank to therebymaintain a mapping of the HARQ process (for which the bundled NACKmessage was received) to the respective transmission and receptionlayers for both the initial transmission and subsequentretransmission(s).

As shown in FIG. 9, base station processor 101 may select a downlink(DL) transmission rank for subsequent downlink transmissions to wirelessterminal 200 responsive to downlink transmission rank requests and/orrecommendations received from wireless terminal 200 over a feedbackchannel, but base station processor 101 may select a different DLtransmission rank if retransmission of any bundled data blocks isrequired responsive to a HARQ NACK message received for a bundled HARQprocess. When a request/recommendation for a new DL transmission rank isreceived from wireless terminal 200 at block 901, base station processor101 may determine at block 903 if retransmission of any bundled datablocks to wireless terminal 200 is required. More particularly, two datablocks may be transmitted using a same TFRE over transmission/receptionlayers sharing a HARQ process, and if either or both data block(s) faildecoding at wireless terminal 200, a shared/bundled HARQ NACK messagefrom wireless terminal 200 may request retransmission of the two datablocks.

If no retransmission is required at block 903 (e.g., if all previouslytransmitted data blocks using shared/bundled HARQ processes have eitherbeen acknowledged with ACKs or retransmitted a maximum number of allowedtimes), base station processor 101 may proceed with the requested and/orrecommended DL transmission rank at block 907. If retransmission ofpreviously transmitted data blocks using a shared/bundled HARQprocess(es) is required at block 903, however, base station processor101 may select a DL transmission rank at block 905 to maintain HARQprocess mapping for any such retransmissions. DL transmission rankselection of block 905 will be discussed in greater detail below withrespect to the mapping tables of FIGS. 10-13. Once all previously failedbundled data blocks have either been successfully transmitted (asindicated by a HARQ ACK message) or retransmitted a maximum allowednumber of times at block 903, base station processor 101 may thenproceed with the requested and/or recommended DL transmission rank atblock 907.

The mapping tables of FIGS. 10-13 illustrate base station processor 101operations to select transmission rank according to embodimentsincluding four transmission/reception layers with two HARQ processesidentified as HARQ-1 and HARQ-2. By way of example, first transmissionand reception layers TL1 and RL1 may be implemented using TB1, CE1, IM1,SS1, DM1, SB1, and/or CD1 of FIGS. 4 and 5; second transmission andreception layers TL2 and RL2 may be implemented using TB2, CE2, IM2,SS2, DM2, SB2, and/or CD2 of FIGS. 4 and 5; third transmission andreception layers TL3 and RL3 may be implemented using TB3, CE3, IM3,SS3, DM3, SB3, and/or CD3 of FIGS. 4 and 5; and fourth transmission andreception layers TL4 and RL4 may be implemented using TB4, CE4, IM4,SS4, DM4, SB4, and/or CD4 of FIGS. 4 and 5. Moreover, first HARQ processHARQ-1 may map only (without bundling/sharing) to first transmission andreception layers TL1 and RL1 for rank 1 and rank 2 transmissions, andfirst HARQ process HARQ-1 may map (with bundling/sharing) to both firstand second transmission/reception layers TL1, RL1, TL2, and RL2 for rank3 and rank 4 downlink transmissions. Second HARQ process HARQ-2 may maponly (without bundling/sharing) to third transmission and receptionlayers TL3 and RL3 for rank 2 and rank 3 downlink transmissions, andsecond HARQ process HARQ-2 may map (with bundling/sharing) to both thirdand fourth transmission/reception layers TL3, RL3, TL4, and RL4 for rank4 transmissions. For rank 1 downlink transmissions, second HARQ processHARQ-2 may be unused.

In each of the tables of FIGS. 10-13, the “Initial Transmission” headingidentifies the status of the most recent HARQ-ACK/NACK message (receivedfrom wireless terminal 200) corresponding to the most recent downlinktransmission for the respective HARQ process (i.e., HARQ-1 and/orHARQ-2). More particularly, P (pass) represents a HARQ ACK messagereceived for the respective HARQ process representing successfuldecoding of all of the data block or blocks associated with the HARQprocess, F (fail) represents a HARQ NACK message received for therespective HARQ process representing unsuccessful decoding of any onedata block or blocks associate with the HARQ process, and “--”represents non-use of the HARQ process (e.g., HARQ-2 may be unused forrank 1 downlink transmissions). The “UE reported rank” headingidentifies a requested/recommended downlink transmission rank (alsoreferred to as a rank) reported by wireless terminal 200, and the“Scheduled Rank” heading identified a downlink transmission rankactually scheduled by base station processor 101. The “Retransmission”HARQ-1 column identifies whether a new transmission of a new transportdata block or blocks (NT) is allowed for the respective HARQ process,whether a retransmission of a previously transmitted data block orblocks (OT) is to be performed for the respective HARQ process, orwhether no transmission (“--”) is to be performed for the respectiveHARQ process.

The table of FIG. 10 illustrates base station processor 101 rankschedulings when an initial rank 1 downlink transmission is performedusing the first HARQ process HARQ-1 mapped to firsttransmission/reception layers TL1 and RL1. Accordingly, the initialtransmission includes only a single data block transmitted/receivedusing transmission/reception layers TL1 and RL1, and the resultingACK/NACK message for the HARQ-1 process maps to only the single datablock (i.e., an ACK message is generated if the single data block passesdecoding at CD1, or a NACK message is generated if the single data blockfails decoding at CD1). In each case where the single data block passesP (i.e., rows 1, 3, 5, and 7 of FIG. 10) decoding (so that an ACKmessage is received), base station processor 101 may schedule the rankrecommended/requested by wireless terminal 200, and new data NT may betransmitted in accordance with the UE reported rank. With scheduled rank4, new first and second data blocks may be transmitted over respectivetransmission/reception layers TL1/RL1 and TL2/RL2 bundled with HARQ-1using a same TFRE, and new third and fourth data blocks may betransmitted over respective transmission/reception layers TL3/RL3 andTL4/RL4 bundled with HARQ-2 using the same TFRE as shown in row 1 ofFIG. 10. With scheduled rank 3, new first and second data blocks may betransmitted over respective transmission/reception layers TL1/RL1 andTL2/RL2 bundled with HARQ-1 using a same TFRE, and a new third datablock may be transmitted over respective transmission/reception layersTL3/RL3 using HARQ-2 without bundling using the same TFRE as shown inrow 3 of FIG. 10. With scheduled rank 2, a new first data block may betransmitted over transmission/reception layers TL1/RL1 using HARQ-1without bundling using a TFRE, and a second data block may betransmitted over transmission/reception layers TL3/RL3 using HARQ-2without bundling using the TFRE as shown in row 5 of FIG. 10. Withscheduled rank 1, a new first data block may be transmitted overtransmission/reception layers TL1/RL1 using HARQ-1 without bundlingusing the TFRE, and HARQ-2 may remain unused during the TFRE as shown inrow 7 of FIG. 10.

In cases where the single data block fails F (rows 2, 4, 6, and 8 ofFIG. 10) decoding (so that a NACK message is received), base stationprocessor 101 may consider the reported rank, but base station processor101 may schedule the downlink transmission rank to maintain a HARQprocess mapping to support the retransmission of the failed data block.As shown at rows 2, 4, and 6 of FIG. 10, if wireless terminal 200reports a higher rank (i.e., a reported rank of 2, 3, or 4 with aninitial rank of 1), base station processor 101 may allow scheduling of arank 2 transmission to maintain a mapping of HARQ-1 only (withoutbundling/sharing) to transmission/reception layers TL1 and RL1 for theretransmission of the initially failed data block (OT) using a TFREwhile allowing transmission of a new data block (NT) using a mapping ofHARQ-2 only (without bundling/sharing) to transmission/reception layersTL3 and RL3 using the TFRE. In an alternative to scheduling rank 2 atrows 2, 4, and 6 of FIG. 10, base station processor 101 may schedulerank 1 to retransmit the failed data block maintaining a mapping ofHARQ-1 only to transmission/reception layers TL1 and RL1 withouttransmitting a new data block using HARQ-2. If the reported rank is thesame as the initial rank as shown in row 8 of FIG. 10, the scheduledrank may remain unchanged so that the mapping of HARQ-1 totransmission/reception layers TL1/RL1 is unchanged and so that thefailed data block may be retransmitted using the same HARQ-1 mapping.

The table of FIG. 11 illustrates base station processor 101 rankschedulings when an initial rank 2 downlink transmission is performedusing the first HARQ process HARQ-1 mapped to firsttransmission/reception layers TL1 and RL1 (without bundling/sharing) andusing the second HARQ process HARQ-2 mapped to thirdtransmission/reception layers TL3 and RL3 (without bundling/sharing).Accordingly, the initial transmission includes a first data blocktransmitted/received using transmission/reception layers TL1 and RL1 anda second data block transmitted/received using transmission/receptionlayers TL3 and RL3. The resulting ACK/NACK message for the HARQ-1process maps to only the first data block (i.e., an ACK message isgenerated if the first data block passes decoding at CD1, or a NACKmessage is generated if the single data block fails decoding at CD1),and the resulting ACK/NACK message for the HARQ-2 process maps to onlythe second data block (i.e., an ACK message is generated if the seconddata block passes decoding at CD3, or a NACK message is generated if thesecond data block fails decoding at CD3).

In each case where both of the first and second data blocks pass P(i.e., rows 1, 5, 9, and 13) decoding (so that two ACK messages arereceived), base station processor 101 may schedule the rankrecommended/requested by wireless terminal 200, and new data NT may betransmitted in accordance with the UE reported rank. With scheduled rank4, new first and second data blocks may be transmitted over respectivetransmission/reception layers TL1/RL1 and TL2/RL2 bundled with HARQ-1using a same TFRE, and new third and fourth data blocks may betransmitted over respective transmission/reception layers TL3/RL3 andTL4/RL4 bundled with HARQ-2 using the same TFRE as shown in row 1 ofFIG. 11. With scheduled rank 3, new first and second data blocks may betransmitted over respective transmission/reception layers TL1/RL1 andTL2/RL2 bundled with HARQ-1 using a same TFRE, and a new third datablock may be transmitted over respective transmission/reception layersTL3/RL3 using HARQ-2 without bundling using the same TFRE as shown inrow 5 of FIG. 11. With scheduled rank 2, a new first data block may betransmitted over transmission/reception layers TL1/RL1 using HARQ-1without bundling using a TFRE, and a second data block may betransmitted over transmission/reception layers TL3/RL3 using HARQ-2without bundling using the TFRE as shown in row 9 of FIG. 11. Withscheduled rank 1, a new first data block may be transmitted overtransmission/reception layers TL1/RL1 using HARQ-1 without bundlingusing the TFRE, and HARQ-2 may remain unused during the TFRE as shown inrow 13 of FIG. 11.

In each case where wireless terminal 200 reports a recommended/requestedrank 2 that is the same as the initial rank (as in rows 9, 10, 11, and12 of FIG. 11), base station processor 101 may maintain the samescheduled rank (i.e., rank 2) regardless of the pass/fail status of theinitially transmitted data blocks. The same rank 2 HARQ process mappingsfor HARQ-1 and HARQ-2 are maintained for the nexttransmission/retransmission regardless of the status P/F of the initialrank 2 transmission. Accordingly, retransmissions of one or both of thefirst and second data blocks (OT) may be supported using the same HARQmappings, and/or new data blocks may be transmitted for either or bothHARQ processes for which initial decoding passed.

When wireless terminal 200 reports a higher rank (i.e., rank 3 or rank4) and the first data block (mapped to HARQ-1 without bundling/sharing)of the initial transmission fails F decoding resulting in a HARQ-1 NACKmessage (as in rows 3, 4, 7, and 8 of FIG. 11), base station processor101 may select rank 2 to maintain the same downlink transmission rank.The same rank 2 HARQ process mappings for HARQ-1 and HARQ-2 are thusmaintained for the retransmission of the first data block that failedand for the possible retransmission of the second data block usingHARQ-2 if it failed or the transmission of a new data block using HARQ-2if the initial second data block passed. According to one alternative ofrow 7 of FIG. 11, base station processor 101 may schedule a lower rank 1transmission if the second data block of HARQ-2 passed to supportretransmission of the first data block of HARQ-1 without transmitting anew data block using HARQ-2.

When wireless terminal 200 reports a higher rank (i.e., rank 3 or rank4), when the first data block (mapped to HARQ-1 withoutbundling/sharing) of the initial transmission passes P decoding, andwhen the second data block (mapped to HARQ-2 without bundling/sharing)of the initial transmission fails F decoding resulting in a HARQ-2 NACKmessage (as in rows 2 and 6 of FIG. 11), base station processor 101 mayselect rank 3 (at rows 2 and 6 of FIG. 11) to maintain the same HARQ-2mapping to transmission/reception layers TL3/RL3 (withoutsharing/bundling) while allowing HARQ-1 to be mapped totransmission/reception layers TL1/RL1 and TL2/RL2 to allow transmissionof two new data blocks NT using the HARQ-1 process. Stated in otherwords, a higher rank may be allowed even though the second data blockfailed because the mapping of HARQ-2 to transmission/reception layersTL3/RL3 (without sharing/bundling) is the same for both rank 2 and rank3 transmissions. While the mapping of HARQ-1 is different for rank 2 andrank 3 transmissions, a same mapping of HARQ-1 is not required becausethe initial HARQ-1 data block passed. Accordingly, a higher data raterank 3 transmission (allowing retransmission of the one HARQ-2 datapacked that failed and 2 new HARQ-1 data packets) may be allowed whilesupporting the HARQ-2 retransmission.

At row 14 of FIG. 11, if the first data block (of HARQ-1) of the initialtransmission passes (P), if the second data block (HARQ-2) of theinitial transmission fails (F), and wireless terminal 200 reports rank1, base station processor may schedule an alternative rank onetransmission retransmitting the second data block of the initialtransmission using HARQ-2 (without bundling/sharing) overtransmission/reception layers TL3/RL3. In an alternative at row 14 ofFIG. 11, rank 2 may be scheduled to support transmission of a new datablock over transmission/reception layers TL1/RL1 using HARQ-1 andretransmission of the second data block over transmission/receptionlayers TL3/RL3 using HARQ-2.

At row 15 of FIG. 11, if the first data block (of HARQ-1) of the initialtransmission fails (F), if the second data block (HARQ-2) of the initialtransmission passes (P), and wireless terminal 200 reports rank 1, basestation processor 101 may schedule a conventional rank one transmissionretransmitting the first data block of the initial transmission usingHARQ-1 (without bundling/sharing) over transmission/reception layersTL1/RL1. At row 16 of FIG. 11, if both of the first data block (HARQ-1)and the second data block (HARQ-2) of the initial transmission fail (F)and wireless terminal 200 reports rank 1, base station processor 101 mayforce a rank 2 transmission to maintain the mappings of HARQ-1 totransmission/reception layers TL1/RL1 and HARQ-2 totransmission/reception layers TL3/RL3 for retransmissions of both of thefailed data blocks.

The table of FIG. 12 illustrates base station processor 101 rankschedulings when an initial rank 3 downlink transmission is performedusing the first HARQ process HARQ-1 mapped to first and secondtransmission/reception layers TL1/RL1 and TL2/RL2 (withbundling/sharing) and using the second HARQ process HARQ-2 mapped tothird transmission/reception layers TL3/RL3 (without bundling/sharing).Accordingly, the initial transmission includes a first data blocktransmitted/received using transmission/reception layers TL1/RL1, andsecond data block transmitted/received using transmission/receptionlayers TL2/RL2, and a third data block transmitted/received usingtransmission/reception layers TL3/RL3. The resulting ACK/NACK messagefor the HARQ-1 process thus maps to the first and second data blocks(i.e., an ACK message is generated if both the first and second datablocks pass decoding at CD1 and CD2, or a NACK message is generated ifeither or both of the first and second data block fail decoding at CD1/CD2), and the resulting ACK/NACK message for the HARQ-2 process maps toonly the third data block (i.e., an ACK message is generated if thethird data block passes decoding at CD3, or a NACK message is generatedif the third data block fails decoding at CD3).

If each of the first, second, and third data blocks pass decoding sothat both HARQ-1 and HARQ-2 pass P (i.e., so two ACK messages arereceived), base station processor 101 may schedule the rankrecommended/requested by wireless terminal 200 (as in rows 1, 5, 9, and13 of FIG. 12), and new data NT may be transmitted in accordance withthe UE reported rank. With scheduled rank 4, new first and second datablocks may be transmitted over respective transmission/reception layersTL1/RL1 and TL2/RL2 bundled with HARQ-1 using a same TFRE, and new thirdand fourth data blocks may be transmitted over respectivetransmission/reception layers TL3/RL3 and TL4/RL4 bundled with HARQ-2using the same TFRE as shown in row 5 of FIG. 12. With scheduled rank 3,new first and second data blocks may be transmitted over respectivetransmission/reception layers TL1/RL1 and TL2/RL2 bundled with HARQ-1using a same TFRE, and a new third data block may be transmitted overrespective transmission/reception layers TL3/RL3 using HARQ-2 withoutbundling using the same TFRE as shown in row 1 of FIG. 12. Withscheduled rank 2, a new first data block may be transmitted overtransmission/reception layers TL1/RL1 using HARQ-1 without bundlingusing a TFRE, and a second data block may be transmitted overtransmission/reception layers TL3/RL3 using HARQ-2 without bundlingusing the TFRE as shown in row 9 of FIG. 12. With scheduled rank 1, anew first data block may be transmitted over transmission/receptionlayers TL1/RL1 using HARQ-1 without bundling using the TFRE, and HARQ-2may remain unused during the TFRE as shown in row 13 of FIG. 12.

In each case where wireless terminal 200 reports a recommended/requestedrank 3 that is the same as the initial rank (as in rows 1, 2, 3, and 4of FIG. 13), base station processor 101 may maintain the same scheduledrank (i.e., rank 3). The same rank 2 HARQ process mappings for HARQ-1and HARQ-2 are maintained for the next transmission/retransmissionregardless of the status P/F of the initial rank 3 transmission.Accordingly, retransmissions of the first and second data blocks (OT) ofHARQ-1 and/or retransmission of the third data block (OT) of HARQ-2 maybe supported using the same HARQ mappings, and/or new data blocks may betransmitted for either or both HARQ processes for which initial decodingpassed.

When wireless terminal 200 reports a higher rank (i.e., rank 4) and thethird data block (mapped to HARQ-2 without bundling/sharing) of theinitial transmission fails F decoding resulting in a HARQ-2 NACK message(as in rows 6 and 8 of FIG. 12), base station processor 101 may maintainrank 3 to maintain the same rank 3 HARQ process mappings for HARQ-1 andHARQ-2. Accordingly, any needed retransmissions may be supported.

When wireless terminal 200 reports a higher rank (i.e., rank 4) and thethird data block (mapped to HARQ-2 without bundling/sharing) of theinitial transmission passes decoding resulting in a HARQ-2 ACK message(as in rows 5 and 7 of FIG. 12), base station processor 101 may schedulerank 4 so that HARQ-1 is mapped to transmission/reception layers TL1/RL1and TL2/RL2 and so that HARQ-2 is mapped to transmission/receptionlayers TL3/RL3 and TL4/RL4. Here the HARQ-1 mapping is unchanged betweenrank 3 and rank 4 to support retransmission of first and second datablocks mapped to HARQ-1 if needed as shown at row 7 of FIG. 12.

When wireless terminal 200 reports rank 2 and the first and second datablocks (mapped to HARQ-1 with sharing/bundling) pass decoding resultingin a HARQ-1 ACK message (as in rows 9 and 10 of FIG. 12), base stationprocessor 101 may schedule rank 2 so that HARQ-1 is mapped totransmission/reception layers TL1/RL1 (without sharing/bundling) and sothat HARQ-2 is mapped to transmission/reception layers TL3/RL3 (withoutsharing/bundling). Accordingly, a mapping of HARQ-2 totransmission/reception layers TL3/RL3 is the same for rank 2 and rank 3downlink transmissions. Because both of the first and second data blocksof the initial HARQ-1 transmission passed decoding, retransmission usingthe HARQ-1 process is not required and remapping of the HARQ-1 processcan occur without affecting any HARQ-1 retransmissions.

When wireless terminal 200 reports rank 2 and either or both of thefirst and second data blocks (mapped to HARQ-1 with sharing/bundling)fail decoding (F) resulting in a HARQ-1 NACK message (as in rows 11 and12 of FIG. 12), base station processor 101 may continue scheduling rank3 (as in rows 11 and 12 of FIG. 12) so that mappings of HARQ-1 andHARQ-2 remain unchanged (i.e., HARQ-1 maps to transmission/receptionlayers TL1/RL1 and TL2/RL2 and HARQ-2 maps to transmission/receptionlayer TL3/RL3). Accordingly, retransmissions of first and second datablocks of HARQ-1 may be supported, and retransmission of third datablock of HARQ-2 may be supported if needed (at row 12 of FIG. 12).

At row 14 of FIG. 12, if the first and second data blocks (mapped toHARQ-1) of the initial transmission pass (P), if the third data block(mapped to HARQ-2) of the initial transmission fails (F), and wirelessterminal 200 reports rank 1, base station processor 101 may schedule analternative rank one transmission retransmitting the third data block ofthe initial transmission using HARQ-2 (without bundling/sharing) overtransmission/reception layers TL3/RL3. In another alternative at row 14,base station processor may schedule a conventional rank 2 transmissionso that a new data block may be transmitted using transmission/receptionlayers TL1/RL1 and HARQ-1 and so that the third data block may be may beretransmitted.

At rows 15 and 16 of FIG. 12, if either or both of the first data blocks(mapped to HARQ-1) of the initial transmission fails (F), and wirelessterminal 200 reports rank 1, base station processor 101 may continuescheduling rank 3 to support retransmission of the first and second datablocks that are mapped to HARQ-1.

The table of FIG. 13 illustrates base station processor 101 rankschedulings when an initial rank 4 downlink transmission is performedusing the first HARQ process HARQ-1 mapped to first and secondtransmission/reception layers TL1/RL1 and TL2/RL2 (withbundling/sharing) and using the second HARQ process HARQ-2 mapped tothird and fourth transmission/reception layers TL3/RL3 and TL4/RL4 (withbundling/sharing). Accordingly, the initial transmission includes afirst data block transmitted/received using transmission/receptionlayers TL1/RL1, and second data block transmitted/received usingtransmission/reception layers TL2/RL2, a third data blocktransmitted/received using transmission/reception layers TL3/RL3, and afourth data block transmitted using transmission/reception layersTL4/RL4. The resulting ACK/NACK message for the HARQ-1 process thus mapsto the first and second data blocks (i.e., an ACK message is generatedif both the first and second data blocks pass decoding at CD1 and CD2,or a NACK message is generated if either or both of the first and seconddata block fail decoding at CD1/CD2), and the resulting ACK/NACK messagefor the HARQ-2 process maps to the third and fourth data blocks (i.e.,an ACK message is generated if both the third and fourth data blockspass decoding at CD3 and CD4, or a NACK message is generated if eitheror both of the third and fourth data blocks fail decoding at CD3/CD4).

In each case where all of the first, second, third and fourth datablocks pass decoding so that both HARQ-1 and HARQ-2 pass P (i.e., so twoACK messages are received), base station processor 101 may schedule therank recommended/requested by wireless terminal 200 (as in rows 1, 5, 9,and 13 of FIG. 13), and new data NT may be transmitted in accordancewith the UE reported rank. With scheduled rank 4, new first and seconddata blocks may be transmitted over respective transmission/receptionlayers TL1/RL1 and TL2/RL2 bundled with HARQ-1 using a same TFRE, andnew third and fourth data blocks may be transmitted over respectivetransmission/reception layers TL3/RL3 and TL4/RL4 bundled with HARQ-2using the same TFRE as shown in row 1 of FIG. 13. With scheduled rank 3,new first and second data blocks may be transmitted over respectivetransmission/reception layers TL1/RL1 and TL2/RL2 bundled with HARQ-1using a same TFRE, and a new third data block may be transmitted overrespective transmission/reception layers TL3/RL3 using HARQ-2 withoutbundling using the same TFRE as shown in row 5 of FIG. 13. Withscheduled rank 2, a new first data block may be transmitted overtransmission/reception layers TL1/RL1 using HARQ-1 without bundlingusing a TFRE, and a second data block may be transmitted overtransmission/reception layers TL3/RL3 using HARQ-2 without bundlingusing the TFRE as shown in row 9 of FIG. 13. With scheduled rank 1, anew first data block may be transmitted over transmission/receptionlayers TL1/RL1 using HARQ-1 without bundling using the TFRE, and HARQ-2may remain unused during the TFRE as shown in row 13 of FIG. 13.

In each case where wireless terminal 200 reports a recommended/requestedrank 4 that is the same as the initial rank (as in rows 1, 2, 3, and 4of FIG. 13), base station processor 101 may maintain the same scheduledrank (i.e., rank 4). The same rank 4 HARQ process mappings for HARQ-1and HARQ-2 are maintained for the next transmission/retransmissionregardless of the status P/F of the initial rank 4 transmission.Accordingly, retransmissions of the first and second data blocks (OT) ofHARQ-1 and/or retransmission of the third and fourth data blocks (OT) ofHARQ-2 may be supported using the same HARQ mappings, and/or new datablocks may be transmitted for either or both HARQ processes for whichinitial decoding passed.

When wireless terminal 200 reports a lower rank (e.g., rank 3, rank 2,or rank 1) and either or both of the third or fourth data blocks (mappedto HARQ-2 with sharing/bundling) fail decoding F resulting in a HARQ-2NACK message (as in rows 6, 8, 10, 12, 14, or 16 of FIG. 13), basestation processor 101 may continue scheduling rank 4 so that HARQ-2 ismapped to the third and fourth transmission/reception layers TL3/RL3 andTL4/RL4 to support retransmission of the third and fourth data blocks.By continuing rank 4, HARQ-1 may continue to be mapped totransmission/reception layers TL1/RL1 and TL2/RL2 to supportretransmission of the first and second data blocks (mapped to HARQ-1with sharing/bundling) if needed (e.g., at rows 8, 12, or 16 of FIG.13), or two new data blocks may be transmitted using HARQ-1 (e.g., atrows 6, 10, or 14 of FIG. 13).

When wireless terminal 200 reports rank 3 and the third and fourth datablocks (mapped to HARQ-2 with sharing/bundling) pass decoding Presulting in a HARQ-2 ACK message (as in rows 5 and 7 of FIG. 13), basestation processor 101 may scheduling rank 3 so that HARQ-1 is mapped tothe first and second transmission/reception layers TL1/RL1 and TL2/RL2(with bundling/sharing) to support retransmission of the first andsecond data blocks if needed, and so that HARQ-2 is mapped to the thirdtransmission/reception layer TL3/RL3 (without bundling/sharing).

When wireless terminal 200 reports rank 2 and either or both of thefirst and second data blocks (mapped to HARQ-1 with sharing/bundling)fail decoding resulting in a HARQ-1 NACK message and both of the thirdand fourth data blocks (mapped to HARQ-2) pass decoding resulting in aHARQ-2 ACK (as in row 11 of FIG. 13), base station processor 101 mayschedule rank 3 so that HARQ-1 is mapped to transmission/receptionlayers TL1/RL1 and TL2/RL2 (with sharing/bundling) and so that HARQ-2 ismapped to transmission/reception layers TL3/RL3 (withoutsharing/bundling). Accordingly, a mapping of HARQ-1 totransmission/reception layers TL1/RL1 and TL2/RL2 is the same for rank 3and rank 4 downlink transmissions to support retransmission of the firstand second data blocks. Because both of the third and fourth data blocksof the initial HARQ-2 transmission passed decoding, retransmission usingthe HARQ-2 process is not required and remapping of the HARQ-2 processcan occur without affecting any HARQ-2 retransmissions.

When wireless terminal 200 reports rank 1 and either or both of thefirst and second data blocks (mapped to HARQ-1 with sharing/bundling)fail decoding (F) resulting in a HARQ-1 NACK message and both of thethird and fourth data blocks (mapped to HARQ-2 with sharing/bundling)pass decoding (P) resulting in a HARQ-2 ACK messages at in row 15 ofFIG. 13, base station processor 101 may schedule rank 3 so that mappingsof HARQ-1 remain unchanged (i.e., HARQ-1 maps to transmission/receptionlayers TL1/RL1 and TL2/RL2). Accordingly, retransmissions of first andsecond data blocks of HARQ-1 may be supported, and HARQ-2 may be mappedto transmission/reception layers TL1/RL1 (without bundling/sharing) fortransmission of a new data block.

As set forth in the tables of FIGS. 10-13, P may represent an ACK forthe respective HARQ process, and F may represent a NACK for therespective HARQ process. Moreover, NT (new transmission) represents anew transmission of a new data block(s), and OT (old transmission)represents a retransmission of a previously transmitted data block(s)for which the associate HARQ process generated a NACK.

According to embodiments discussed above, radio base station processor101 may select a MIMO transmission rank for a subsequent downlinktransmission responsive to a rank reported (e.g., requested/recommended)by wireless terminal 200, but base station processor 101 may deviatefrom the reported rank if a NACK has been received for one or more HARQprocesses used for a preceding downlink transmission. More particularly,wireless terminal 200 may deviate from the reported rank to select aMIMO transmission rank that maintains a HARQ process mapping from thepreceding downlink transmission if the HARQ process generated a NACK forthe preceding downlink transmission. When two HARQ processes are used ina 4 antenna system supporting up to 4 downlink data streams (i.e., up torank 4), for example, if an initial downlink transmission has rank 2 orhigher and both HARQ processes generate NACKs, base station processor101 may maintain the same rank for the next transmission (even if alower or a higher rank was reported) to support retransmission of alldata blocks of both HARQ processes (see, rows 4, 8, 12, and 16 of FIG.11; rows 4, 8, 12, and 16 of FIG. 12; and rows 4, 8, 12, and 16 of FIG.13). If all HARQ processes used in an initial downlink transmissiongenerate ACKs, base station processor 101 may change the rank for thenext transmission to any rank reported by wireless terminal 200 (see,rows 1, 3, 5, 7 of FIG. 10; rows 1, 5, 9, and 13 of FIG. 11; rows 1, 5,9, and 13 of FIG. 12; and rows 1, 5, 9, and 13 of FIG. 13). If abundled/shared HARQ process used in an initial downlink transmissiongenerates a NACK, base station processor 101 may require a rank of threeor higher for the next transmission.

According to some embodiments, a first transmission/reception layer(corresponding to a stream of data codewords CW1) may be supported usingTB1, CE1, IM1, and/or SS1 at base station 100 and using DM1, SB1, and/orCD1 at wireless terminal 200; a second transmission/reception layer(corresponding to a stream of data codewords CW2) may be supported usingTB2, CE2, IM2, and/or SS2 at base station 100 and using DM2, SB2, and/orCD2 at wireless terminal 200; a third transmission/reception layer(corresponding to a stream of data codewords CW3) may be supported usingTB3, CE3, IM3, and/or SS3 at base station 100 and using DM3, SB3, and/orCD3 at wireless terminal 200; and a fourth transmission/reception layer(corresponding to a stream of data codewords CW4) may be supported usingTB4, CE4, IM4, and/or SS4 at base station 100 and using DM4, SB4, and/orCD4 at wireless terminal 200. As shown in FIG. 14 for rank 1transmission/reception, a single stream of data codewords CW1 may betransmitted/received using the first transmission/reception layer (e.g.,including TB1, CE1, IM1, and/or SS1 at base station 100 and includingDM1, SB1, and/or CD1 at wireless terminal 200) without using the second,third, and fourth transmission/reception layers, and a first HARQprocess/codeword (HARQ-1) may be mapped directly to the single stream ofdata codewords CW1. As shown in FIG. 14 for rank 2transmission/reception, a first stream of data codewords CW1 may betransmitted/received using the first transmission/reception layer (e.g.,including TB1, CE1, IM1, and/or SS1 at base station 100 and includingDM1, SB1, and/or CD1 at wireless terminal 200), and a second stream ofdata codewords CW2 may be transmitted/received using the secondtransmission/reception layer (e.g., including TB2, CE2, IM2, and/or SS2at base station 100 and including DM2, SB2, and/or CD2 at wirelessterminal 200), without using the third and fourth transmission/receptionlayers. For rank 2 transmission/reception, the first HARQprocess/codeword (HARQ-1) may be mapped directly to the first stream ofdata codewords CW1, and a second HARQ process/codeword (HARQ-2) may bemapped directly to the second stream of data codewords CW2. For rank 1and 2 transmission/reception of FIG. 14, each stream of codewords may bemapped directly to a respective HARQ process/codeword without bundlingas discussed above.

As shown in FIG. 14 for rank 3 transmission/reception, a first stream ofdata codewords CW1 may be transmitted/received using the firsttransmission/reception layer (e.g., including TB1, CE1, IM1, and/or SS1at base station 100 and including DM1, SB1, and/or CD1 at wirelessterminal 200), a second stream of data codewords CW2 may betransmitted/received using the second transmission/reception layer(e.g., including TB2, CE2, IM2, and/or SS2 at base station 100 andincluding DM2, SB2, and/or CD2 at wireless terminal 200), and a thirdstream of data codewords CW3 may be transmitted/received using the thirdtransmission/reception layer (e.g., including TB3, CE3, IM3, and/or SS3at base station 100 and including DM3, SB3, and/or CD3 at wirelessterminal 200), without using the fourth transmission/reception layer.For rank three transmission/reception, the first HARQ process/codeword(HARQ-1) may be mapped directly to the first stream of data codewordsCW1, while the second HARQ process/codeword (HARQ-2) may be mapped toboth of the second and third streams of data codewords CW2 and CW3. Forrank 3 transmission/reception, the first stream of codewords may bemapped directly to the first HARQ process/codeword without bundling,while the second and third streams of codewords may be bundled with thesecond HARQ process.

As shown in FIG. 14 for rank 4 transmission/reception, a first stream ofdata codewords CW1 may be transmitted/received using the firsttransmission/reception layer (e.g., including TB1, CE1, IM1, and/or SS1at base station 100 and including DM1, SB1, and/or CD1 at wirelessterminal 200), a second stream of data codewords CW2 may betransmitted/received using the second transmission/reception layer(e.g., including TB2, CE2, IM2, and/or SS2 at base station 100 andincluding DM2, SB2, and/or CD2 at wireless terminal 200), a third streamof data codewords CW3 may be transmitted/received using the thirdtransmission/reception layer (e.g., including TB3, CE3, IM3, and/or SS3at base station 100 and including DM3, SB3, and/or CD3 at wirelessterminal 200), and a fourth stream of data codewords Cw4 may betransmitted/received using the fourth transmission/reception layer(e.g., including TB4, CE4, IM4, and/or SS4 at base station 100 andincluding DM4, SB4, and/or CD4 at wireless terminal 200). Moreover, thefirst HARQ process/codeword (HARQ-1) may be mapped to both of the firstand fourth streams of data codewords CW1 and CW4, and the second HARQprocess/codeword (HARQ-2) may be mapped to both of the second and thirdstreams of data codewords CW2 and CW3. For rank 4transmission/reception, the first and second streams of codewords may bebundled with first HARQ process/codeword, while the second and thirdstreams of codewords may be bundled with the second HARQ process.

According to embodiments of FIG. 14, the first transmission/receptionlayer TL1/RL1 (transmitted using TB1, CE1, IM1, and/or SS1 at basestation 100 and received using DM1, SB1, and/or CD1 at wireless terminal200) may support transmission/reception of data codewords CW1, and thefirst transmission layer may be mapped to the first HARQ process(HARQ-1) for transmission according to ranks 1, 2, 3, and 4. The secondtransmission/reception layer TL1/RL1 (transmitted using TB2, CE2, IM2,and/or SS2 at base station 100 and received using DM2, SB2, and/or CD2at wireless terminal 200) may support transmission/reception of datacodewords CW2, and the second transmission layer may be mapped to thesecond HARQ process (HARQ-2) for transmission according to ranks 2, 3,and 4. The third transmission/reception layer TL3/RL3 (transmitted usingTB2, CE3, IM3, and/or SS3 at base station 100 and received using DM3,SB3, and/or CD3 at wireless terminal 200) may supporttransmission/reception of data codewords CW3, and the third transmissionlayer may be mapped to the second HARQ process (HARQ-2) for transmissionaccording to ranks 3 and 4. The fourth transmission/reception layerTL4/RL4 (transmitted using TB4, CE4, IM4, and/or SS4 at base station 100and received using DM4, SB4, and/or CD4 at wireless terminal 200) maysupport transmission/reception of data codewords CW4, and the fourthtransmission layer may be mapped to the second HARQ process (HARQ-2) fortransmission according to rank 4. Accordingly, eachtransmission/reception layer (when used) is mapped to a same HARQprocess regardless of the transmission/reception rank being use.Accordingly, each wireless terminal decoder and soft buffer may bemapped to a same HARQ processes for any rank using the decoder and softbuffer.

According to embodiments of FIG. 14: a mapping of layer 1 to the firstHARQ process HARQ-1 remains the same for ranks 1, 2, 3, and 4; a mappingof layer 2 to the second HARQ process HARQ-2 remains the same for ranks2, 3, and 4; and a mapping of layer 3 to the second HARQ process HARQ-2remains the same for ranks 3 and 4. Accordingly, if the rank changesbetween ranks 3 and 4, the bundled mapping of layers 2 and 3 to thesecond HARQ process HARQ-2 stays the same, thereby supportingretransmissions over layers 2 and 3 while changing to either rank 3 orrank 4 with HARQ 2 bundled to the 2^(nd) and 3^(rd) layers. Similarly,if the rank changes between ranks 1 and 2, between ranks 2 and 3, orbetween ranks 1 and 3, the direct mapping of layer 1 to the first HARQprocess HARQ-1 stays the same, thereby supporting retransmissions overlayer 1 while changing to rank 1, rank 2, or rank 3 with HARQ-1 bundledto the first layer (without bundling). Partial retransmission (e.g.,where previously transmitted data for one HARQ process is retransmittedand new data for the other HARQ process is initially transmitted duringthe same TTI) may thus be supported while changing rank as long as thelayer or layers mapped to the HARQ process for the retransmission isunchanged.

Wireless terminal processor 201 and/or transceiver 209 may define aplurality of reception layers/streams as discussed above with respect toFIGS. 4 and/or 5: with a first layer RL1 being used for MIMO ranks 1, 2,3, and 4; with a second layer RL2 being used for MIMO ranks 2, 3, and 4;with a third layer RL3 being used for MIMO ranks 3 and 4; and with afourth MIMO layer RL4 being used for MIMO rank 4. Separate decoding(e.g., using decoder functionally illustrated by decoders CD1-4 of FIG.5) may be performed for each MIMO layer received during a MIMO TTI.Wireless terminal processor 201, for example, may define, configure,and/or use one or more of reception layers RL1, RL2, RL3, and/or RL4 fora given TTI/TFRE responsive to rank and/or precoding vector informationprovided from base station 100 via downlink signaling as discussed abovewith respect to FIG. 3A. For example, a higher MIMO rank (defining arespective higher number of reception layers/streams) may be selectedwhen the wireless terminal detects that the downlink channel has ahigher SINR (e.g., when the wireless terminal is relatively close to thebase station), and a lower MIMO rank (defining a respective lower numberof reception layers/streams) may be selected when the wireless terminaldetects that the downlink channel has a lower SINR (e.g., when thewireless terminal is relatively distant from the base station).

While separate transport block generator, encoder, modulator, layermapper, spreader/scrambler, and layer precoder blocks are illustrated inFIG. 4 by way of example, the blocks of FIG. 4 merely illustratefunctionalities/operations of base station processor 101 and/ortransceiver 109. Sub-blocks (e.g., transport blocks TB1-TB4 channelencoders CE1-CE4, interleavers/modulators IM1-IM4, and spreaderscramblers SS1-SS4) of FIG. 4 further illustratefunctionalities/operations of transport block generator, encoder block,modulator block, and spreader/scrambler block supporting transmissionlayers TL1-TL4. Processor 101, however, may provide/define/configurefunctionality/operations of only one transmission layer TL1 during rank1 transmission; processor 101 may provide/define/configurefunctionality/operations of only two transmission layers TL1 and TL2during rank 2 transmission; processor 101 may provide/define/configurefunctionality/operations of only 3 transmission layers TL1, TL2, and TL3during rank 3 transmission; and functionality/operations of fourtransmission layers TL1, TL2, TL3, and TL4 may only be provided duringrank 4 transmission. When multiple transmission layers areprovided/defined/configured, for example, processor 101 mayprovide/define/configure functionality/operations of multiple transportblock sub-blocks, multiple channel decoder sub-blocks, multipleinterleaver/modulator sub-blocks, and/or multiple spreader/scramblersub-blocks to allow parallel processing of data of differenttransmission layers before transmission during a TTI/TFRE, or processor101 may provide/define/configure functionality/operations of a singletransport block, a single channel encoder, a singleinterleaver/modulator, and/or a single spreader scrambler to allowserial processing of data of different transmission layers beforetransmission during a TTI/TFRE.

While separate layer decoder, layer demapper, demodulator/deinterleaver,soft buffer, channel decoder, and transport block combinerblocks/sub-blocks are illustrated in FIG. 5 by way of example, theblocks of FIG. 5 merely illustrate functionalities/operations ofwireless terminal processor 201 and/or transceiver 209. For example,sub-blocks (e.g., demodulator/deinterleaver DM1-DM4, soft buffersSB1-SB4, and channel decoders CD1-CD4) of FIG. 5 illustratefunctionalities/operations providing reception layers RL1-RL4. Processor101, however, may provide/define/configure functionality/operations ofonly one reception layer RL1 during rank 1 reception; processor 101 mayprovide/define/configure functionality/operations of only two receptionlayers RL1 and RL2 during rank 2 transmission; processor 101 mayprovide/define/configure functionality/operations of only 3 receptionlayers RL1, RL2, and RL3 during rank 3 transmission; andfunctionality/operations of four reception layers RL1, RL2, RL3, and RL4may only be provided during rank 4 transmission. When multiple receptionlayers are provided/defined/configured, for example, processor 101 mayprovide/define/configure functionality/operations of multipledemodulator/deinterleaver blocks, multiple soft buffer blocks, and/ormultiple channel decoder blocks to allow parallel processing of data ofdifferent reception layers during a TTI/TFRE, or processor 101 mayprovide/define/configure functionality/operations of a singledemodulator/deinterleaver block, a single soft buffer, and/or a singlechannel decoder to allow serial processing of data of differentreception layers during a TTI/TFRE.

According to embodiments discussed above with respect to FIG. 14, basestation processor 101 may use mapping tables of FIGS. 10-13 toretransmit failed data packets (e.g., associated with a bundled HARQprocess) as an alternative to using mapping tables of FIGS. 15-18 asdiscussed above with respect to operations of FIG. 9 when wirelessterminal 200 reports/requests a downlink transmission rank that isdifferent than the downlink transmission rank used to initially transmitthe now failed data packets. These embodiments will now be discussed ingreater detail below with respect to the tables of FIGS. 15-18 forsystems including 4 transmit and 4 receive MIMO antennas supporting one,two, three, and four MIMO transmission ranks. While embodiments relatingto 4 transmit and 4 receive MIMO antennas are discussed by way ofexample, embodiments may be applied to systems including fewer and/ormore MIMO transmit and receive antennas.

If retransmission of previously transmitted data blocks using ashared/bundled HARQ process(es) is required at block 903 of FIG. 9, basestation processor 101 may select a DL transmission rank at block 905 tomaintain a same HARQ process mapping for any such retransmissions as setforth in the tables of FIGS. 15-18. The headings, acronyms, andabbreviations of FIGS. 15-18 have the same meanings as those discussedabove with respect to FIGS. 10-13.

The table of FIG. 15 illustrates base station processor 101 rankschedulings when an initial rank 1 downlink transmission is performedusing the first HARQ process HARQ-1 mapped to firsttransmission/reception layers TL1/RL1. Accordingly, the initialtransmission includes only a single data block transmitted/receivedusing transmission/reception layers TL1/RL1, and the resulting ACK/NACKmessage for the HARQ-1 process maps to only the single data block (i.e.,an ACK message is generated if the single data block passes decoding atCD1, or a NACK message is generated if the single data block failsdecoding at CD1). In each case where the single data block passes P(i.e., rows 1, 3, 5, and 7 of FIG. 15) decoding (so that an ACK messageis received), base station processor 101 may schedule the rankreported/requested by wireless terminal 200, and new data NT may betransmitted in accordance with the UE reported rank. With scheduled rank4, new first and fourth data blocks may be transmitted over respectivetransmission/reception layers TL1/RL1 and TL4/RL4 bundled with HARQ-1using a same TFRE, and new second and third data blocks may betransmitted over respective transmission/reception layers TL2/RL2 andTL3/RL3 bundled with HARQ-2 using the same TFRE as shown in row 1 ofFIG. 15. With scheduled rank 3, a new first data block may betransmitted over respective transmission/reception layers TL1/RL1 usingHARQ-1 using a TFRE without bundling, and new second and third datablocks may be transmitted over respective transmission/reception layersTL2/TL2 and TL3/RL3 bundled with HARQ-2 using the same TFRE as shown inrow 3 of FIG. 15. With scheduled rank 2, a new first data block may betransmitted over transmission/reception layers TL1/RL1 using HARQ-1without bundling using a TFRE, and a second data block may betransmitted over transmission/reception layers TL2/RL2 using HARQ-2without bundling using the TFRE as shown in row 5 of FIG. 15. Withscheduled rank 1, a new first data block may be transmitted overtransmission/reception layers TL1/RL1 using HARQ-1 without bundlingusing the TFRE, and HARQ-2 may remain unused during the TFRE as shown inrow 7 of FIG. 15.

In cases where the single data block fails F (rows 2, 4, 6, and 8 ofFIG. 15) decoding (so that a NACK message is received), base stationprocessor 101 may consider the reported rank, but base station processor101 may schedule the downlink transmission using the reported rank or adifferent rank to maintain a HARQ process mapping to support theretransmission of the failed data block. As shown at rows 2, 4, and 6 ofFIG. 15, for example, if wireless terminal 200 reports a rank higherthan that of the initial transmission (i.e., a reported rank of 2, 3, or4 with an initial rank of 1), base station processor 101 may allowscheduling of a higher rank transmission but not necessarily the rankreported/requested by wireless terminal 200. As shown at rows 4 and 6 ofFIG. 15, if wireless terminal 200 reports/requests a rank of 3 or 2after a failed rank 1 transmission/reception, base station processor 101may schedule the reported/requested rank (i.e., rank 3 or 2) because theHARQ-1 is mapped to the first transmission/reception layer TL1/RL1without bundling for rank 1, 2, and 3 transmission/reception accordingto embodiments of FIG. 14. As shown at row 2 of FIG. 15, if wirelessterminal 200 reports/requests a rank of 4 after a failed rank 1transmission/reception, base station processor 101 may schedule a rank 3transmission (higher than the previous rank 1 transmission) because arank 3 transmission maintains the mapping of the firsttransmission/reception layer TL1/RL1 to HARQ-1 without bundling tosupport retransmission (in contrast to a rank 4 transmission that wouldbundle HARQ-1). If the reported rank is the same as the initial rank asshown in row 8 of FIG. 15, the scheduled rank may remain unchanged sothat the mapping of HARQ-1 to transmission/reception layers TL1/RL1 isunchanged and so that the failed data block may be retransmitted usingthe same HARQ-1 mapping. More generally, if the reported rank isunchanged relative to the initial rank as shown in rows 7 and 8 of FIG.15, the reported rank may be scheduled whether the initial data block(s)was(were) successfully decoded or not.

FIG. 16 illustrates base station processor 101 rank schedulings when aninitial rank 2 downlink transmission is performed using HARQ-1 mapped tofirst transmission/reception layers TL1/RL1 (without bundling/sharing)and using HARQ-2 mapped to second transmission/reception layers TL2/RL2(without bundling/sharing). Accordingly, the initial transmissionincludes a first data block transmitted/received usingtransmission/reception layers TL1/RL1 and a second data blocktransmitted/received using transmission/reception layers TL2/RL2. Theresulting ACK/NACK message for HARQ-1 maps to only the first data block(i.e., an ACK message is generated if the first data block passesdecoding at CD1, or a NACK message is generated if the single data blockfails decoding at CD1), and the resulting ACK/NACK message for theHARQ-2 process maps to only the second data block (i.e., an ACK messageis generated if the second data block passes decoding at CD2, or a NACKmessage is generated if the second data block fails decoding at CD2).

In each case where both of the first and second data blocks pass P(i.e., rows 1, 5, 9, and 13) decoding (so that two ACK messages arereceived), base station processor 101 may schedule the rankrecommended/requested by wireless terminal 200, and new data NT may betransmitted in accordance with the UE reported rank as discussed abovewith respect to rows 1, 3, 5, and 7 of FIG. 15. In each case wherewireless terminal 200 reports/recommends rank 2 that is the same as theinitial rank (as in rows 9, 10, 11, and 12 of FIG. 11), base stationprocessor 101 may maintain the same scheduled rank (i.e., rank 2)regardless of the pass/fail status of the initially transmitted datablocks. The same rank 2 HARQ process mappings for HARQ-1 and HARQ-2 aremaintained for the next transmission/retransmission regardless of thestatus P/F of the initial rank 2 transmission. Accordingly,retransmissions of one or both of the first and second data blocks (OT)may be supported using the same HARQ mappings, and/or new data blocksmay be transmitted for either or both HARQ processes for which initialdecoding passed.

When wireless terminal 200 reports a higher rank (i.e., rank 3 or rank4) and the second data block (mapped to HARQ-2 without bundling/sharing)of the initial transmission fails F decoding resulting in a HARQ-2 NACKmessage (as in rows 2, 4, 6, and 8 of FIG. 16), base station processor101 may select rank 2 to maintain the same downlink transmission rank.The same rank 2 HARQ process mappings for HARQ-1 and HARQ-2 are thusmaintained for the retransmission of the second data block using HARQ-2that failed and for the possible retransmission of the first data blockusing HARQ-1 if it failed or the transmission of a new data block usingHARQ-1 if the initial first data block passed.

When wireless terminal 200 reports a higher rank (i.e., rank 3 or rank4), when the second data block (mapped to HARQ-2 withoutbundling/sharing) of the initial transmission passes P decoding, andwhen the first data block (mapped to HARQ-1 without bundling/sharing) ofthe initial transmission fails F decoding resulting in a HARQ-1 NACKmessage (as in rows 3 and 7 of FIG. 16), base station processor 101 mayselect rank 3 (at rows 3 and 7 of FIG. 16) to maintain the same HARQ-1mapping to transmission/reception layers TL1/RL1 (withoutsharing/bundling) while allowing HARQ-2 to be mapped totransmission/reception layers TL2/RL2 and TL3/RL3 to allow transmissionof two new data blocks NT using the HARQ-2 process. Stated in otherwords, a higher rank may be allowed even though the first data blockfailed because the mapping of HARQ-1 to transmission/reception layersTL1/RL1 (without sharing/bundling) is the same for both rank 2 and rank3 transmissions. While the mapping of HARQ-2 is different for rank 2 andrank 3 transmissions, a same mapping of HARQ-2 is not required becausethe initial HARQ-2 data block passed. Accordingly, a higher data raterank 3 transmission (allowing retransmission of the one HARQ-1 datapacket that failed and 2 new HARQ-2 data packets) may be allowed whilesupporting the HARQ-1 retransmission.

At row 14 of FIG. 16, if the first data block (of HARQ-1) of the initialtransmission passes (P), if the second data block (of HARQ-2) of theinitial transmission fails (F), and wireless terminal 200 reports rank1, base station processor 101 may schedule a rank two transmission tosupport transmission of a new data block over transmission/receptionlayers TL1/RL1 using HARQ-1 and retransmission of the second data blockover transmission/reception layers TL2/RL2 using HARQ-2. At row 15 ofFIG. 16, if the first data block (of HARQ-1) of the initial transmissionfails (F), if the second data block (HARQ-2) of the initial transmissionpasses (P), and wireless terminal 200 reports rank 1, base stationprocessor 101 may schedule a rank one transmission retransmitting thefirst data block of the initial transmission using HARQ-1 (withoutbundling/sharing) over transmission/reception layers TL1/RL1. At row 16of FIG. 16, if both of the first data block (HARQ-1) and the second datablock (HARQ-2) of the initial transmission fail (F) and wirelessterminal 200 reports rank 1, base station processor 101 may force a rank2 transmission to maintain the mappings of HARQ-1 totransmission/reception layers TL1/RL1 and HARQ-2 totransmission/reception layers TL2/RL2 for retransmissions of both of thefailed data blocks.

FIG. 17 illustrates base station processor 101 rank schedulings when aninitial rank 3 downlink transmission is performed using HARQ-1 mapped tofirst transmission/reception layers TL1/RL1 (without bundling/sharing)and using HARQ-2 mapped to second and third transmission/receptionlayers TL2/TL2 and TL3/RL3 (with bundling/sharing). Accordingly, theinitial transmission includes a first data block transmitted/receivedusing transmission/reception layers TL1/RL1, a second data blocktransmitted/received using transmission/reception layers TL2/RL2, and athird data block transmitted/received using transmission/receptionlayers TL3/RL3. The resulting ACK/NACK message for HARQ-1 thus maps tothe first data block (i.e., an ACK message is generated if the firstdata block passes decoding at CD1, or a NACK message is generated if thefirst data block fails decoding at CD1), and the resulting ACK/NACKmessage for the HARQ-2 process maps to the second and third data blocks(i.e., an ACK message is generated if both of the second and third datablock pass decoding at CD2 and CD3, or a NACK message is generated ifeither of the second and/or third data blocks fail decoding at CD2and/or CD3).

In cases where each of the first, second, and third data blocks passdecoding so that both HARQ-1 and HARQ-2 pass P (i.e., so two ACKmessages are received), base station processor 101 may schedule the rankrecommended/requested by wireless terminal 200 (as in rows 1, 5, 9, and13 of FIG. 17), and new data NT may be transmitted in accordance withthe UE reported rank as discussed above with respect to FIGS. 15 and 16.In each case where wireless terminal 200 reports a recommended/requestedrank 3 that is the same as the initial rank (as in rows 5, 6, 7, and 8of FIG. 13), base station processor 101 may maintain the same scheduledrank (i.e., rank 3). The same rank 3 HARQ process mappings for HARQ-1and HARQ-2 are thus maintained for the next transmission/retransmissionregardless of the status P/F of the initial rank 3 transmission.Accordingly, retransmission of the first data block (OT) of HARQ-1and/or retransmission of the second and third data blocks (OT) of HARQ-2may be supported using the same HARQ mappings, and/or new data blocksmay be transmitted for either or both HARQ processes for which initialdecoding passed.

When wireless terminal 200 reports a higher rank (i.e., rank 4) and thefirst data block (mapped to HARQ-1 without bundling/sharing) of theinitial transmission fails F decoding resulting in a HARQ-1 NACK message(as in rows 3 and 4 of FIG. 17), base station processor 101 may maintainrank 3 to maintain the same rank 3 HARQ process mappings for HARQ-1 andHARQ-2. Accordingly, any needed retransmissions may be supported. Whenwireless terminal 200 reports a higher rank (i.e., rank 4) and the firstdata block (mapped to HARQ-1 without bundling/sharing) of the initialtransmission passes decoding resulting in a HARQ-1 ACK message (as inrows 1 and 2 of FIG. 17), base station processor 101 may schedule rank 4so that HARQ-1 is mapped to transmission/reception layers TL1/RL1 andTL4/RL4 and so that HARQ-2 is mapped to transmission/reception layersTL2/RL2 and TL3/RL3. Here the HARQ-2 mapping is unchanged between rank 3and rank 4 to support retransmission of second and third data blocksmapped to HARQ-2 if needed as shown at row 2 of FIG. 17.

When wireless terminal 200 reports rank 2 and the second and third datablocks (mapped to HARQ-2 with sharing/bundling) pass decoding resultingin a HARQ-2 ACK message (as in rows 9 and 11 of FIG. 17), base stationprocessor 101 may schedule rank 2 so that HARQ-1 is mapped totransmission/reception layers TL1/RL1 (without sharing/bundling) and sothat HARQ-2 is mapped to transmission/reception layers TL2/RL2 (withoutsharing/bundling). Accordingly, a mapping of HARQ-1 totransmission/reception layers TL1/RL1 is the same for rank 2 and rank 3downlink transmissions. Because both of the second and third data blocksof the initial HARQ-2 transmission passed decoding, retransmission usingthe HARQ-2 process is not required and remapping of the HARQ-2 processcan occur without affecting any HARQ-2 retransmissions.

When wireless terminal 200 reports rank 2 and either or both of thesecond and third data blocks (mapped to HARQ-2 with sharing/bundling)fail decoding (F) resulting in a HARQ-2 NACK message (as in rows 10 and12 of FIG. 17), base station processor 101 may continue scheduling rank3 (as in rows 10 and 12 of FIG. 17) so that mappings of HARQ-1 andHARQ-2 remain unchanged (i.e., HARQ-1 maps to transmission/receptionlayers TL1/RL1 and HARQ-2 maps to transmission/reception layers TL2/RL2and TL3/RL3). Accordingly, retransmissions of second and third datablocks of HARQ-2 may be supported, and retransmission of a first datablock of HARQ-1 may be supported if needed (at row 12 of FIG. 17).

At rows 13 and 15 of FIG. 17, if the second and third data blocks(mapped to HARQ-2) of the initial transmission pass (P) and wirelessterminal 200 reports rank 1, base station processor may schedule a rank1 transmission supporting transmission of new data or retransmission ofold data using the first transmission/reception layers RL1/TL1. At rows14 and 16 of FIG. 17, if either of the second and/or third data blocks(mapped to HARQ-2) of the initial transmission fail (F) and wirelessterminal 200 reports rank 1, base station processor 101 mayschedule/maintain rank 3 transmission to support retransmission of thesecond and/or third data blocks using transmission/reception layersRL2/TL2 and RL3/TL3 mapped to HARQ-2.

The table of FIG. 18 illustrates base station processor 101 rankschedulings when an initial rank 4 downlink transmission is performedusing HARQ-1 mapped to first and fourth transmission/reception layersTL1/RL1 and TL4/RL4 (with bundling/sharing) and using HARQ-2 mapped tosecond and third transmission/reception layers TL2/RL2 and TL3/RL3 (withbundling/sharing). Accordingly, the initial transmission includes afirst data block transmitted/received using transmission/receptionlayers TL1/RL1, a second data block transmitted/received usingtransmission/reception layers TL2/RL2, a third data blocktransmitted/received using transmission/reception layers TL3/RL3, and afourth data block transmitted using transmission/reception layersTL4/RL4. The resulting ACK/NACK message for HARQ-1 thus maps to thefirst and fourth data blocks (i.e., an ACK message is generated if boththe first and fourth data blocks pass decoding at CD1 and CD4, or a NACKmessage is generated if either or both of the first and fourth datablocks fail decoding at CD1/CD4), and the resulting ACK/NACK message forHARQ-2 maps to the second and third data blocks (i.e., an ACK message isgenerated if both the second and third data blocks pass decoding at CD2and CD3, or a NACK message is generated if either or both of the secondand third data blocks fail decoding at CD2/CD3).

In each case where all of the first, second, third and fourth datablocks pass decoding so that both HARQ-1 and HARQ-2 pass P (i.e., so twoACK messages are received), base station processor 101 may schedule therank reported/requested by wireless terminal 200 (as in rows 1, 5, 9,and 13 of FIG. 18), and new data NT may be transmitted in accordancewith the UE reported rank as discussed above with respect to FIGS. 15,16, and 17. In each case where wireless terminal 200 reports arecommended/requested rank 4 that is the same as the initial rank (as inrows 1, 2, 3, and 4 of FIG. 18), base station processor 101 may maintainthe same scheduled rank (i.e., rank 4). The same rank 4 HARQ processmappings for HARQ-1 and HARQ-2 are thus maintained for the nexttransmission/retransmission regardless of the status P/F of the initialrank 4 transmission. Accordingly, retransmissions of the first andfourth data blocks (OT) of HARQ-1 and/or retransmission of the secondand third data blocks (OT) of HARQ-2 may be supported using the sameHARQ mappings, and/or new data blocks may be transmitted for either orboth HARQ processes for which initial decoding passed.

When wireless terminal 200 reports a lower rank (e.g., rank 3, rank 2,or rank 1) and either or both of the first and fourth data blocks(mapped to HARQ-1 with sharing/bundling) fail decoding F resulting in aHARQ-1 NACK message (as in rows 7, 8, 11, 12, 15, or 16 of FIG. 18),base station processor 101 may continue scheduling rank 4 so that HARQ-1is mapped to the first and fourth transmission/reception layers TL1/RL1and TL4/RL4 to support retransmission of the first and fourth datablocks. By continuing rank 4, HARQ-2 may continue to be mapped totransmission/reception layers TL2/RL2 and TL3/RL3 to supportretransmission of the second and third data blocks (mapped to HARQ-2with sharing/bundling) if needed (e.g., at rows 8, 12, or 16 of FIG.18), or two new data blocks may be transmitted using HARQ-2 (e.g., atrows 7, 11, or 15 of FIG. 18).

When wireless terminal 200 reports rank 3 and the first data block(mapped to HARQ-1 without sharing/bundling) passes decoding P resultingin a HARQ-1 ACK message (as in rows 5 and 6 of FIG. 18), base stationprocessor 101 may scheduling rank 3 so that HARQ-1 is mapped to thefirst transmission/reception layers TL1/RL1 (without bundling/sharing),and so that HARQ-2 is mapped to the second and thirdtransmission/reception layers RL2/TL2 and TL3/RL3 (withbundling/sharing) to support retransmission of the second and third datablocks if needed (e.g., at row 6 of FIG. 18).

When wireless terminal 200 reports rank 2 and any of the first, second,third, and/or fourth data blocks fail decoding resulting in a HARQ-1NACK and/or a HARQ-2 NACK (as in rows 10, 11, and/or 12), base stationprocessor 101 may schedule rank 4 so that HARQ-1 is mapped totransmission/reception layers RL1/TL1 and RL4/TL4 (withbundling/sharing) and HARQ-2 is mapped to transmission/reception layersRL2/TL2 and RL3/TL3 (with bundling/sharing). Accordingly, mappings ofHARQ-1 to transmission/reception layers TL1/RL1 and TL4/RL4 and HARQ-2to transmission/reception layers RL2/TL2 and RL3/TL3 are maintained tosupport retransmissions as needed.

When wireless terminal 200 reports rank 1 and any of the first, second,third, and/or fourth data blocks fail decoding (F) resulting in a HARQ-1NACK and/or a HARQ-2 NACK message (as in rows 14, 15, and/or 16), basestation processor 101 may schedule rank 4 so that HARQ-1 is mapped totransmission/reception layers RL1/TL1 and RL4/TL4 (withbundling/sharing) and HARQ-2 is mapped to transmission/reception layersRL2/TL2 and RL3/TL3 (with bundling/sharing). Accordingly, mappings ofHARQ-1 to transmission/reception layers TL1/RL1 and TL4/RL4 and HARQ-2to transmission/reception layers RL2/TL2 and RL3/TL3 are maintained tosupport retransmissions as needed.

According to embodiments discussed above with respect to FIGS. 14-18,when an initial transmission/reception has a rank greater than 1 (e.g.,rank 2, 3, or 4) and both HARQ processes pass (i.e., both HARQ-1 andHARQ-2 generate ACK messages), base station processor 101 may select therank reported/requested by wireless terminal 200 for a subsequenttransmission to wireless terminal 100. When an initialtransmission/reception has a rank greater than 1 (e.g., rank 2, 3, or 4)and both HARQ processes fail (i.e., HARQ-1 and HARQ-2 generate NACKmessages), base station processor 101 may maintain the rank used for theinitial transmission (regardless of the rank reported/requested bywireless terminal 200) to support retransmission of data blockscorresponding to HARQ-1 and HARQ-2.

If an initial transmission is a rank 2 transmission so that an initialdata block transmitted/received over transmission/reception layersRL2/TL2 and mapped to HARQ-2 without bundling, and if HARQ-2 generates aNACK due to failure decoding the initial data block, base stationprocessor 101 may restrict the next transmission to rank 2 (regardlessof the rank reported/requested by wireless terminal 200) to supportretransmission of the data block over transmission/reception layersRL2/TL2 as shown in rows 2, 4, 6, 8, 10, 12, 14, and 16 of FIG. 16because no other rank (e.g., rank 1, 3, or 4) supports non-bundled useof transmission/reception layers RL2/TL2. Stated in other words, if adata block is mapped to a HARQ process without bundling and the datablock fails decoding, the same rank may be maintained for retransmission(regardless of the rank reported/requested by wireless terminal) if noother rank supports non-bundled transmission/reception using the sametransmission/reception layer.

Using mappings of FIGS. 15-18, bundled transport blocks sharing a sameHARQ process that fail decoding during an initial transmission may thusbe retransmitted using the same transmission/reception layers bundled tothe same HARQ process.

Base station operations for shared HARQ processes have been discussedabove with respect to FIGS. 8A and 9-18 where a base station 100transmit buffer (e.g., included in base station processor 101 and/ormemory 118) for wireless terminal 200 is not buffer limited (e.g., thetransmit buffer includes sufficient data for wireless terminal 200 for anext transmission data block or blocks). Stated in other words, a basestation transmit buffer for wireless terminal 200 is not buffer limitedwhen it includes new data for one or more new transport data blocks (NTas shown in the tables of FIGS. 10-13 and 15-18) to be transmitted towireless terminal 200. In the event that downlink transmission towireless terminal 200 is buffer limited (e.g., sufficient new data isnot available for new transport data blocks NT to be sent to wirelessterminal 200) when a partial retransmission is called for responsive toreceiving both a NACK and an ACK for a rank 2 or higher MIMO TTI,however, an additional mechanism(s) may be useful to efficiently handlethe retransmission.

In a multicodeword MIMO system with two HARQ codewords supporting morethan two MIMO layers/ranks, if one HARQ codeword is an ACK (or P forpass) and the other HARQ codeword is a NACK (or F for fail), embodimentsdiscussed below may provide a mechanism to retransmit a failed transportdata block or blocks corresponding to the NACK when downlinktransmissions are buffer limited. More particularly, embodimentsdiscussed below may address retransmission of a transport data block orblocks corresponding to the NACK when the base station processor 101(e.g., a transmit buffer of the base station processor 101 for wirelessterminal 200) is buffer limited (e.g., the transmit buffer does not haveenough data to transmit a transport data block or blocks on the MIMOlayer or layers corresponding to the ACK). This situation may occur, forexample, at the end of a communication/session/call with/for wirelessterminal 200 when a base station transmit buffer for wireless terminal200 is empty or when downlink transmissions are not continuous, and aretransmission is needed responsive to a NACK. While embodiments arediscussed for systems including 4 transmit and 4 receive antennassupporting up to 4 MIMO layers, embodiments may be applied in anymulti-antenna system supporting rank 2 and/or higher MIMOtransmission/reception.

According to some embodiments illustrated in FIGS. 19 and 20A-C, when aNACK and an ACK are received from wireless terminal 200 at base station100 for a rank 2 or higher downlink MIMO TTI and the base station 100 istransmit buffer limited with respect to wireless terminal 200 (e.g.,there is insufficient buffered data for a new transport data block orblocks for the MIMO layer or layers corresponding to the ACK), basestation 200 may maintain the same rank for retransmission of thetransport data block or blocks corresponding to the NACK during a secondMIMO TTI. The transport data block or blocks corresponding to the NACKmay thus be retransmitted during the second MIMO TTI over the same MIMOlayer or layers used during the first MIMO TTI. Instead ofretransmitting the transport data block or blocks corresponding to theACK during the second MIMO TTI, however, base station 200 may transmitan indication of discontinuous transmission (DTX) over the downlinksignaling channel (e.g., HS-SCCH) informing wireless terminal 200 thatno data will be transmitted over the MIMO layers corresponding to theACK.

FIG. 19 is a flow chart illustrating base station operations supportingretransmission in response to a NACK or NACKs indicating failuredecoding at wireless terminal 200. As shown in the flow chart of FIG. 19at block 1899, base station processor 101 may transmit one or moretransport data blocks over respective MIMO layers (also referred to asMIMO streams) during a first MIMO transmission time interval (TTI), alsoreferred to as a Time Frequency Resource Element or TFRE. While a 4antenna system supporting up to four MIMO layers will be discussed byway of example, embodiments may be applied to any multi-antenna MIMOsystems supporting rank 2 or higher MIMO transmission/reception (e.g.,an 8 antenna system supporting up to eight MIMO layers/streams). For arank 1 MIMO transmission of a 4 antenna system, base station processor101 may transmit one transport data block over a first MIMO layer duringthe first MIMO TTI, and a first HARQ process (HARQ-1) may map to thefirst transport data block of the first MIMO layer. For a rank 2 MIMOtransmission of a 4 antenna system, base station processor 101 maytransmit first and second transport data blocks over respective firstand second MIMO layers/streams during the first MIMO TTI, and first andsecond HARQ processes (HARQ-1 and HARQ-2) may map to the respectivefirst and second transport data blocks of the respective first andsecond MIMO layers. For a rank 3 MIMO transmission of a 4 antennasystem, base station processor 101 may transmit first, second, and thirdtransport data blocks over respective first, second, and third MIMOlayers during the first MIMO TTI, the first HARQ process may map to thefirst transport data block of the first MIMO layer, and the second HARQprocess may map to the second and third transport data blocks of therespective second and third MIMO layers. For a rank 4 MIMO transmissionof a 4 antenna system, base station processor 101 may transmit first,second, third, and fourth transport data blocks over respective first,second, third, and fourth MIMO layers during the first MIMO TTI, thefirst HARQ process may map to the first and fourth transport data blocksof the respective the first and fourth MIMO layers, and the second HARQprocess may map to the second and third transport data blocks of therespective second and third MIMO layers.

As discussed above, wireless terminal 200 generates an ACK or a NACK foreach HARQ process used during the first MIMO TTI. If all transport datablocks that map to a HARQ process for the first TTI are successfullydecoded by wireless terminal 200, wireless terminal 200 transmits an ACKfor that HARQ process. If any one of the transport data blocks that mapsto a HARQ process for the first TTI is not successfully decoded bywireless terminal 200, wireless terminal 200 transmits a NACK for thatHARQ process. At block 1901, base station processor 101 receives HARQprocess feedback (i.e., ACKs/NACKs) from wireless terminal 200 for eachHARQ process used during the 1^(st) TTI. If the 1^(st) MIMO TTI was arank 1 TTI used to transmit one transport data block, an ACK is receivedfor the first HARQ process if the transport data block was successfullydecoded, or a NACK is received for the first HARQ process if thetransport data block is not successfully decoded. The second HARQprocess is not used for a rank 1 TTI. If the 1^(st) MIMO TTI was a rank2 TTI used to transmit first and second transport data blocks, an ACK isreceived for the first HARQ process if the first transport data blockwas successfully decoded or a NACK is received for the first HARQprocess if the first transport data block is not successfully decoded,and an ACK is received for the second HARQ process if the secondtransport data block was successfully decoded or a NACK is received forthe second HARQ process if the second transport data block was notsuccessfully decoded. If the 1^(st) MIMO TTI was a rank 3 TTI used totransmit first, second, and third transport data blocks, an ACK isreceived for the first HARQ process if the first transport data blockwas successfully decoded or a NACK is received for the first HARQprocess if the first transport data block was not successfully decoded,and an ACK is received for the second HARQ process if the second andthird transport data blocks were both successfully decoded or a NACK isreceived for the second HARQ process if either or both of the secondand/or third transport data blocks was not successfully decoded. If the1^(st) MIMO TTI was a rank 4 TTI used to transmit first, second, third,and fourth transport data blocks, an ACK is received for the first HARQprocess if the first and fourth transport data blocks were successfullydecoded or a NACK is received for the first HARQ process if either orboth of the first and/or second transport data blocks was notsuccessfully decoded, and an ACK is received for the second HARQ processif the second and third transport data blocks were successfully decodedor a NACK is received for the second HARQ process if either or both ofthe second and/or third transport data blocks was not successfullydecoded.

At block 1903 and/or at block 1905, if the 1^(st) MIMO TTI was a rank 1TTI and/or if base station 100 is not transmit buffer limited withrespect to wireless terminal 200, base station processor 101 may proceedat block 1915 with operations according to embodiments of FIGS. 8A, 9,10, 11, 12, 13, 14, 15, 16, 17, and/or 18 as discussed above. Otherwise,if the 1^(st) MIMO TTI was a rank 2 or higher TTI and the base stationprocessor is transmit buffer limited at blocks 1903 and 1905, basestation processor 101 may proceed to block 2107.

At block 2107, if ACKs are received for all HARQ processes used in the1^(st) MIMO TTI, there is no need for retransmission and there is nodata (or insufficient data) in the transmit buffer to schedule a newMIMO TTI for wireless terminal 200 (i.e., base station 100 was deemed tobe transmit buffer limited with respect to wireless terminal 200 atblock 1905). Accordingly, no downlink signaling or traffic istransmitted to wireless terminal 200 over downlink signaling or trafficchannels (e.g., HS-SCCH or HS-DPSCH) at block 1917 until further data isreceived in the transmit buffer for wireless terminal 200.

At block 2107, if NACKs are received for all HARQ processes used in the1^(st) MIMO TTI, base station processor 101 may generate and transmitdata indicators indicating retransmission (for a second MIMO TTI) of alltransport data blocks that were originally transmitted during the 1^(st)MIMO TTI at block 2109. Moreover, the data indicators indicatingretransmission may be transmitted over a downlink signaling channel(e.g., HS-SCCH). At block 2111, base station processor 101 mayretransmit all of the previously transmitted data blocks from the 1^(st)MIMO TTI during a 2^(nd) MIMO TTI over a downlink traffic channel (e.g.,HS-DPSCH).

At block 2107, if a NACK is received for one HARQ process used in the1^(st) MIMO TTI and an ACK is received for another HARQ process used inthe 1^(st) MIMO TTI, base station processor 101 may generate andtransmit a discontinuous transmission (DTX) indicator (indicating notransmission over MIMO layers corresponding to the ACK) and a dataindicator indicating retransmission of the transport data block orblocks corresponding to the NACK for a 2^(nd) MIMO TTI at block 2121.The DTX indicator and the data indicator indicating retransmission maybe transmitted over a downlink signaling channel (e.g., HS-SCCH). Atblock 2123, base station processor 101 may retransmit the transport datablock or blocks corresponding to the NACK over the MIMO TTI layerscorresponding to the NACK during the 2^(nd) MIMO TTI withoutretransmitting the transport data block or blocks corresponding to theACK. More particularly, the transport data block or blocks correspondingto the NACK may be transmitted over a downlink traffic channel (e.g.,HS-DPSCH) during the 2^(nd) MIMO TTI. By providing the DTX indicatorprior to the retransmission, wireless terminal 200 knows to disregardthe MIMO layer layers corresponding to the ACK during the 2^(nd) MIMOTTI.

FIG. 20A is a retransmission table when the original transmission(1^(st) MIMO TTI) is a rank 4 transmission. As shown in rows 2, 3, 6, 7,10, 11, 14, and 15 of the table of FIG. 20A, when the 1^(st) MIMO TTI isrank 4, base station processor 101 may transmit a discontinuoustransmission DTX indicator for MIMO layers corresponding to the ACK atblock 2121, and base station processor 101 may retransmit only thosetransport data blocks corresponding to a NACK from the 1^(st) MIMO TTIduring the 2^(nd) MIMO TTI as indicated by OT at block 2123. Moreover,base station processor 101 may maintain the MIMO rank of the 1^(st) MIMOTTI (i.e., rank 4) during the 2^(nd) MIMO TTI regardless of the ranksuggested/requested by wireless terminal 200. In an alternative, basestation processor 101 may allow rank 3 (as shown in rows 2, 6, 10, and14 of FIG. 22A) for the 2^(nd) MIMO TTI if the ACK corresponds to thefirst HARQ process (mapped to layers 1 and 4) because rank 3 issufficient to support retransmission of the HARQ-2 data blocks usingMIMO layers 2 and 3. At rows 3, 7, 11, and 15, first and fourthtransport data blocks may be retransmitted over respective first andfourth MIMO layers at block 2123, and at rows 2, 6, 10, and 14, secondand third transport data blocks may be retransmitted over respectivesecond and third MIMO layers at block 2123. As shown in rows 4, 8, 12,and 16 of FIG. 20A, base station processor 101 may retransmit alltransport data blocks from the 1^(st) MIMO TTI during the 2^(nd) MIMOTTI at block 2111 because only NACKs are received for the first MIMOTTI. For example, first, second, third, and fourth transport data blocksmay be retransmitted over respective first, second, third, and fourthtransport data blocks during the 2^(nd) MIMO TTI. As shown in rows 1, 5,9, and 13 of FIG. 20A, there is no transmission/retransmission at block1917 when all ACKs are received and base station 100 is buffer limitedwith respect to wireless terminal 200. When all ACKs are received andbase station 100 is buffer limited with respect to wireless terminal200, no downlink signaling or traffic is transmitted to wirelessterminal 200 over downlink signaling and/or traffic channels (e.g.,HS-SCCH and/or HS-DPSCH) until additional data is received in thetransmit buffer for wireless terminal 200.

FIG. 20B is a retransmission table when the original transmission(1^(st) MIMO TTI) is a rank 3 transmission. As shown in rows 2, 3, 6, 7,10, 11, 14, and 15 of the table of FIG. 20B, when the 1^(st) MIMO TTI isrank 3, base station processor 101 may transmit a discontinuoustransmission DTX indicator for MIMO layers corresponding to the ACK atblock 2121, and base station processor 101 may retransmit only thetransport data block or blocks corresponding to a NACK from the 1^(st)MIMO TTI during the 2^(nd) MIMO TTI as indicated by OT at block 2123.Moreover, base station processor 101 may maintain the MIMO rank of the1^(st) MIMO TTI (i.e., rank 3) during the 2^(nd) MIMO TTI regardless ofthe rank suggested/requested by wireless terminal 200. In analternative, base station processor 101 may allow a different rank (asshown, for example, in parentheses at rows 2, 6, 11, or 15) providedthat the different rank supports transmission/reception using the MIMOlayers corresponding to the NACK. At rows 3, 7, 11, and 15, the firsttransport data block may be retransmitted over the first MIMO layer atblock 2123, and at rows 2, 6, 10, and 14, the second and third transportdata blocks may be retransmitted over respective second and third MIMOlayers at block 2123. As shown in rows 4, 8, 12, and 16 of FIG. 20B,base station processor 101 may retransmit all transport data blocks fromthe 1^(st) MIMO TTI during the 2^(nd) MIMO TTI at block 2111 becauseonly NACKs are received for the first MIMO TTI. For example, first,second, and third transport data blocks may be retransmitted overrespective first, second, and third MIMO layers during the 2^(nd) MIMOTTI. As shown in rows 1, 5, 9, and 13 of FIG. 22B, there is notransmission/retransmission at block 1917 when all ACKs are received andbase station 100 is buffer limited with respect to wireless terminal200. When all ACKs are received and base station 100 is buffer limitedwith respect to wireless terminal 200, no downlink signaling or trafficis transmitted to wireless terminal 200 over downlink signaling and/ortraffic channels (e.g., HS-SCCH and/or HS-DPSCH) until additional datais received in the transmit buffer for wireless terminal 200.

FIG. 20C is a retransmission table when the original transmission(1^(st) MIMO TTI) is a rank 2 transmission. As shown in rows 2, 3, 6, 7,10, 11, 14, and 15 of the table of FIG. 20C, when the 1^(st) MIMO TTI isrank 2, base station processor 101 may transmit a discontinuoustransmission DTX indicator for a MIMO layer corresponding to the ACK atblock 2121, and base station processor 101 may retransmit only thetransport data block corresponding to the NACK from the 1^(st) MIMO TTIduring the 2^(nd) MIMO TTI as indicated by OT at block 2123. Moreover,base station processor 101 may maintain the MIMO rank of the 1^(st) MIMOTTI (i.e., rank 2) during the 2^(nd) MIMO TTI regardless of the ranksuggested/requested by wireless terminal 200. In an alternative, basestation processor 101 may allow a different rank (as shown, for example,in parentheses at rows 3, 7, and 15) provided that the different ranksupports transmission/reception using the MIMO layers corresponding tothe NACK. At rows 3, 7, 11, and 15, the first transport data block maybe retransmitted over the first MIMO layer at block 2123, and at rows 2,6, 10, and 14, the second transport data block may be retransmitted overthe second MIMO layer at block 2123. As shown in rows 4, 8, 12, and 16of FIG. 20C, base station processor 101 may retransmit all transportdata blocks from the 1^(st) MIMO TTI during the 2^(nd) MIMO TTI at block2111 because only NACKs are received for the first MIMO TTI. Forexample, first and second transport data blocks may be retransmittedover respective first and second MIMO layers during the 2^(nd) MIMO TTI.As shown in rows 1, 5, 9, and 13 of FIG. 20C, there is notransmission/retransmission at block 1917 when all ACKs are received andbase station 100 is buffer limited with respect to wireless terminal200. When all ACKs are received and base station 100 is buffer limitedwith respect to wireless terminal 200, no downlink signaling or trafficis transmitted to wireless terminal 200 over downlink signaling and/ortraffic channels (e.g., HS-SCCH and/or HS-DPSCH) until additional datais received in the transmit buffer for wireless terminal 200.

According to embodiments discussed above with respect to FIGS. 19 and20A-C, the discontinuous transmission DTX indicator may be transmittedover a downlink signaling channel such as the HS-SCCH. For example, theDTX indicator may be transmitted as a currently unused bit pattern of a5 bit modulation/rank field of the HS-SCCH, and/or as an unused bitpattern of a 6 bit transport block size field of the HS-SCCH.

FIG. 21A is a block diagram illustrating a structure of an HS-SCCH slotfor a four branch MIMO system (with 4 transmit and 4 receive antennassupporting up to 4 MIMO layers). Part 1 is used to carry informationrelated to a channelization code set, precoding weight information,modulation scheme, and numbers of transport blocks preferred. Part 2 isused to carry information related to transport block size, HARQprocess(es), and redundancy and constellation version. Moreparticularly, FIG. 21A illustrates a Type 4 structure for HS-SCCH.

FIG. 21B is a block diagram illustrating HS-SCCH part 1 for four branchMIMO. For four branch MIMO, Part 1 of HS-SCCH includes 16 bits as shownin FIG. 21B regarding the following information: channelization code setCCS information (7 bits); modulation and rank information MR (5 bits);and precoding index PCI (4 bits). Rank information (RI) may beimplicitly informed through the five bits of the modulation and rankinformation. An identity of wireless terminal 200 may also be signaledin Part 1 through a UE-specific mask applied to the Part 1 encodedsequence. Accordingly, only 16 bits may be needed to the completeinformation of Part 1.

FIG. 21C is a block diagram illustrating HS-SCCH part 2 for four branchMIMO. For four branch MIMO, Part 2 of HS-SCCH may include 36 bits asshown in FIG. 21C regarding the following information: HARQ-1 TransportBlock Size TBS-1 (6 bits); HARQ-2 Transport Block Size TBS-2 (6 bits);HARQ process (4 bits); Redundancy Version RV (4 bits) for the twostreams/layers and/or HARQ processes; and wireless terminalidentification UEID (16 bits). For a single stream/layer (rank 1)transmission using only one HARQ process, Part 2 of HS-SCCH may bereduced to 28 bits.

FIG. 21D is a block diagram illustrating a timing diagram for HS-PDSCHand HS-SCCH transmissions to wireless terminal 200. To allow wirelessterminal 200 enough time to decode the part 1 portion of HS-SCCH (e.g.,HS-SCCH 1) and then configure its receiver to receive the correspondingHS-DPSCH (e.g., HS-DPSCH 1), HS-SCCH 1 may be transmitted 2 slots inadvance of the associated HS-DPSCH 1 subframe as shown in FIG. 21D.

According to some embodiments, the DTX indicator may be transmitted as acurrently unused bit pattern of a 5 bit modulation/rank MR field of theHS-SCCH. FIG. 22 is a table illustrating 5 bit patterns used tocommunicate modulation and rank MR information in HS-SCCH Part 1 asshown in FIG. 21B. In particular, 5 bits may be used to identify 30different combinations of modulations/ranks in a 4 layer MIMO systemwhere two modulation schemes are mapped to the four layers, leaving 2 ofthe bit combinations (e.g., 11110 and 11111) unused. The firstmodulation (Modulation-1) may map to the first HARQ process (HARQ-1) andthus the first and fourth MIMO layers, and the second modulation(Modulation-2) may map to the second HARQ process (HARQ-2) and thus thesecond and third MIMO layers.

FIG. 23 is a table illustrating HS-SCCH combinations for modulation andtransmission rank including use of the previously unused MR bit patterns(e.g., 11110 and 11111) to provide the DTX indicators discussed abovewith respect to FIGS. 19 and 20A-C. For example, the MR bit pattern11110 may be used as a DTX indicator that the first HARQ process willnot be used for retransmission during the second MIMO TTI, and moreparticularly, that the first and fourth MIMO layers will not be used fortransmission/retransmission during the second MIMO TTI. Similarly, theMR bit pattern 11111 may be used as a DTX indicator that the second HARQprocess will not be used for retransmission during the second MIMO TTI,and more particularly, that the second and third MIMO layers will not beused for transmission/retransmission during the second MIMO TTI. Becausebase station processor 101 may maintain the same transmitcharacteristics (e.g., including modulation, rank, and transport blocksize) from the first MIMO TTI during the second MIMO TTI used forretransmission, signaling of the rank and modulation for theretransmission is not required. Stated in other words, the DTXindicators may imply reuse of the modulation and rank information fromthe first MIMO TTI during the retransmission MIMO TTI.

According to some other embodiments, the DTX indicator may betransmitted as a currently unused bit pattern of the transmit block sizeTBS of HS-SCCH for the unused HARQ process. As discussed above withrespect to FIG. 21C, HS-SCCH Part 2 includes a 6 bit TBS field(providing 64 bit combinations) for each HARQ process. Only 63 differenttransport block sizes are defined for a HARQ process, however, leavingone of the 64 bit combinations (e.g., 111111) unused. By setting TBS-1of the HS-SCCH Part 2 slot for the retransmission MIMO TTI to 111111 asa DTX indicator for the first HARQ process, base station processor 101may signal that the first HARQ process will not be used forretransmission during the second MIMO TTI, and more particularly, thatthe first and fourth MIMO layers will not be used fortransmission/retransmission during the second MIMO TTI. By setting TBS-2of the HS-SCCH Part 2 slot for the retransmission MIMO TTI to 111111 asa DTX indicator for the second HARQ process, base station processor 101may signal that the second HARQ process will not be used forretransmission during the second MIMO TTI, and more particularly, thatthe second and third MIMO layers will not be used fortransmission/retransmission during the second MIMO TTI.

Some embodiments may thus provide significant gain without significantlycompromising delay (e.g., avoiding/reducing Radio Link Protocolretransmission).

For rank 2 and higher retransmissions when an ACK message is receivedfor one HARQ process, when a NACK message is received for the other HARQprocess, and when base station processor 101 is transmit buffer limitedwith respect to wireless terminal 200, base station processor 101 maythus transmit a DTX indicator to signal that no data is beingtransmitted/retransmitted using the transmission layer/layerscorresponding to the ACK message. According to some embodimentsdiscussed above with respect to FIGS. 21B and 23, a first unique (andpreviously unused) Modulation and Transmission Rank (modulation-rank orMR) bit pattern (e.g., 11110) may be used to indicate discontinuoustransmission DTX for a transmission layer/layers corresponding to afirst HARQ process, and a second unique (and previously unused)Modulation and Transmission Rank (modulation-rank or MR) bit pattern(e.g., 11111) may be used to indicate discontinuous transmission DTX fora transmission layer/layers corresponding to a second HARQ process.According to some other embodiments discussed above with respect to FIG.21C, a unique and previously unused bit pattern (e.g., 111111) may beused for the respective transport block size TBS corresponding to theACKed HARQ process to indicate discontinuous transmission DTX for atransmission layer/layers corresponding to the ACKed HARQ process. Forexample, the bit pattern 111111 may be used for TBS-1 (fortransmission/reception layers 1 and/or 4) when the first HARQ process isACKed and the second HARQ process is NACKed, and the bit pattern 111111may be used for TBS-2 (for transmission/reception layers 2 and/or 3)when the first HARQ process is NACKed and the second HARQ process isACKed.

A DTX indicator can thus be transmitted by base station processor 101over a downlink signaling channel (HS-SCCH) to indicate discontinuoustransmission over a first MIMO layer/layers corresponding to an ACKmessage when retransmitting over a second MIMO layer/layerscorresponding to a NACK message when base station processor 101 istransmit buffer limited with respect to wireless terminal 200. Inaddition, base station processor 101 may transmit data indicators overthe downlink signaling channel indicating new data transmission over thefirst MIMO layer/layers and indicating retransmission over the secondMIMO layer/layers. More particularly, the data indicators may beprovided in a redundancy version (RV) field of the downlink signalingchannel (HS-SCCH).

In response to receiving such a DTX indicator and data indicators for aretransmission (indicating retransmission for a data block/blockscorresponding to one HARQ process and DTX for a data block/blockscorresponding to another HARQ process), embodiments discussed below mayprovide wireless terminal processor 201 operations to handle datareceived during the retransmission and to transmit feedback informationrelated to the DTXed reception layer/layers.

In general, if a MIMO layer(s) is DTXed during a MIMO TTI (also referredto as a TTI and/or TFRE), then wireless terminal processor 201 maydiscard/disregard data/symbols associated with DTXed MIMO layer/layersfor the TTI, and wireless terminal processor 201 may clear the softbuffer/buffers for the DTXed MIMO layer/layers for the TTI.

When wireless terminal 200 receives a DTX indicator for a first MIMOlayer/layers (e.g., as a unique code in a downlink signaling MR field orin a downlink signaling TBS field), a data indicator for an initialtransmission of the first MIMO layer/layers (e.g., in a downlinksignaling RV field), and data indicator for a retransmission of a secondMIMO layer/layers (e.g., in a downlink signaling RV field), thenwireless terminal processor 201 may discard/disregard data/symbolsreceived over the first MIMO layer/layers, and wireless terminalprocessor 201 may process retransmitted data received over the secondMIMO layer/layers. More particularly, when wireless terminal processor200 receives a DTX indicator and a data indicator for an initialtransmission for a MIMO layer/layers, wireless terminal processor 201may generate and transmit a default HARQ message for the MIMOlayer/layers corresponding to the DTX, discard any received symbols/datafor the DTXed MIMO layer/layers, and assume that the data for the DTXedMIMO layer/layers was successfully decoded in a previous TTI. Accordingto some embodiments, the default HARQ message for a DTXed MIMOlayer/layers may be an ACK message. According to some other embodiments,the default HARQ message for a DTXed MIMO layer/layers may be a NACKmessage. By discarding/disregarding symbols/data for a DTXed MIMOlayer/layers, hardware resource utilization and/or processing overheadmay be reduced.

According to some embodiments, the wireless terminal UE 200 discardsdata and flushes off the soft buffer for a DTXed codeword(s)/layer(s)and the wireless terminal UE 200 does not store data for a DTXedcodeword(s)/layer(s) if a codeword(s)/layers(s) is DTXed. According tosome embodiments:

-   -   1. Whenever a UE received 111111 along with a new data indicator        (either explicit or implicit for example through RV indicator),        then the UE should understand that the corresponding codeword is        DTXed.    -   2. Whenever UE received 111111 along with new data indicator the        UE should,        -   a. Generate a positive acknowledgment (ACK) of the data in            this HARQ process;        -   b. Discard the received data;        -   c. Assume the data had been successfully decoded.            As an alternative to operations 2.a. and 2.b., UE may: (2a)            Generate a negative acknowledgment (NACK) of the data in            this HARQ process, and (2b) discard the received data.

FIG. 24 is a flow chart illustrating operations of wireless terminalprocessor 201 according to some embodiments. At block 2403, processor201 may receive downlink signaling (through antenna array 217 andtransceiver 209) for a MIMO TTI over a downlink signaling channel (e.g.,HS-SCCH). The downlink signaling may be provided, for example, accordingto a format illustrated in FIGS. 21A to 21D. If the downlink signalingindicates that the transmission for the MIMO TTI is a rank 1 MIMOtransmission at block 2405, if the transmission is not a retransmission(indicated by a redundancy version RV field) at block 2408, and/or if noDTX indicator (e.g., included as a TBS code and/or as an MR code) isincluded for the MIMO TTI, wireless terminal processor 201 may receive atransport data block or blocks over a respective MIMO layer or layersduring the MIMO TTI at block 2431. At block 2433, wireless terminalprocessor 201 may generate and transmit a HARQ ACK message for eachactive HARQ process for which all data is successfully decoded, andwireless terminal processor 201 may generate and transmit a HARQ NACKmessage for each active HARQ process for which all data is notsuccessfully decoded.

For rank 2 and higher MIMO transmissions (at block 2405) where downlinksignaling includes a new data indicator and a discontinuous transmission(DTX) indicator (at block 2411) for a first downlinkmultiple-input-multiple-output (MIMO) layer and a retransmission dataindicator (at block 2409) for a second downlink MIMO layer, wirelessterminal processor 201 may generate symbols (D) and/or soft bits (CW)for each MIMO layer of the MIMO TTI at block 2415. For a rank 2 MIMO TTIwith the first layer DTXed, for example, wireless terminal processor 201may generate symbols (D1′) and/or soft bits (CW1′) for a DTXed firstMIMO layer associated with a first HARQ process, and processor 201 maygenerate symbols (D2′) and soft bits (CW2′) for a second MIMO layerassociated with a second HARQ process of a retransmission.

According to some embodiments, the new data indicator for the firstdownlink MIMO layer and the retransmission data indicator for the seconddownlink MIMO layer may be included in a redundancy version (RV) fieldof the downlink signaling. According to some embodiments, thediscontinuous transmission (DTX) indicator for the first downlink MIMOlayer may be a unique transport block size code (e.g., 111111) in atransport block size field of the downlink signaling for the second MIMOlayer. According to some other embodiments, the discontinuoustransmission (DTX) indicator for a first downlink MIMO layer may be aunique modulation-rank code (e.g., 11110 or 11111) in a modulation andtransmission rank (MR) field of the downlink signaling for the secondMIMO layer.

At block 2417, wireless terminal processor 201 may discard/disregardinformation/data/symbols for the layer/layers corresponding to the DTXindicator. In the example of a rank 2 MIMO TTI with a DTX indicator forthe first layer, processor 201 may discard/disregard the symbols for thefirst MIMO layer for the TTI without demodulating and/or decoding thesymbols for the first MIMO layer. According to some other embodiments ina rank 2 MIMO TTI with a DTX indicator for the first layer, processor201 may generate soft bits for the first MIMO layer for the TTIresponsive to the symbols for the first MIMO layer and discard/disregardthe soft bits for the first MIMO layer for the TTI without decoding thesoft bits.

At block 2419, processor 201 may decode the soft bits for thelayer/layers of the retransmission (that were not DTXed). In the exampleof a rank 2 MIMO TTI with a DTX indicator for the first layer, processor201 may decode the soft bits for the second MIMO layer for the TTI.According to some embodiments, processor 201 may decode the soft bitsfor the second MIMO layer for the TTI responsive to the soft bits forthe second MIMO layer for the TTI and responsive to soft bits for thesecond MIMO layer for a previous TTI (that were previously stored insoft buffer SB2).

At block 2421, processor 201 may generate/transmit an ACK or a NACKmessage for the layer/layers of the retransmission responsive tosuccess/failure decoding the soft bits for the layer/layers of theretransmission. In the example of a rank 2 MIMO TTI with a DTX indicatorfor the first layer, processor 201 may generate/transmit (throughtransceiver 209 and antenna array 217) an acknowledgment (ACK) messagefor the second MIMO layer responsive to success decoding the soft bitsfor the second MIMO layer for the TTI, or processor 201 maygenerate/transmit a negative acknowledgment (NACK) message for thesecond MIMO layer responsive to failure decoding the soft bits for thesecond MIMO layer for the TTI.

At block 2423, processor 201 may generate/transmit a default responsefor the layer/layers corresponding to the DTX. According to someembodiments, the default response may be a HARQ ACK message for thelayer/layers corresponding to the DTX, and according to some otherembodiments, the default response may be a HARQ NACK message for thelayer/layers corresponding to the DTX.

At block 2425, processor 201 may process the results of theretransmission. In the example of the rank 2 MIMO TTI, when decoding thesoft bits for the second MIMO layer for the TTI at block 2419 results insuccessfully decoding the soft bits to generate hard bits for the secondMIMO layer for the TTI, processor 201 generates/transmits an ACK messagefor the second MIMO layer at block 2421, and processor 201 combines thehard bits for the second MIMO layer for the TTI with hard bits for thefirst MIMO layer for a previous TTI to provide a received data stream atblock 2425. In the example of the rank 2 MIMO TTI, when decoding thesoft bits for the second MIMO layer for the TTI at block 2419 results inunsuccessfully decoding the soft bits, processor 201 generates/transmitsa NACK message for the second MIMO layer at block 2421, and processor201 saves the soft bits in a soft buffer (SB2) to be used decoding asubsequent retransmission over the second MIMO layer during a subsequentTTI at block 2425.

Embodiments discussed herein may thus define wireless terminaloperations during a retransmission when one HARQ process is ACKed(indicating successful receipt of the transport data block/blocksreceived over the MIMO layer/layers associated with the ACK during theprior transmission) and anther HARQ process is NACKed (indicatingunsuccessful receipt of the transport data block/blocks received overthe MIMO layer/layers associated with the NACK during the priortransmission). While embodiments are discussed above for wirelessterminal (receiver) operations in four transmit/receive antenna systems(supporting up to 4 layer MIMO) in HSDPA by way of example, embodimentsmay be implemented using higher or lower order antenna systems (e.g.,two transmit/receive antenna systems supporting up to 2 layer MIMO, oreight transmit/receive antenna systems supporting up to 8 layer MIMO)and/or using other radio access technologies (e.g., LTE/LTE-A, WiMax,etc.). Moreover, while rank 2 retransmissions are discussed by way ofexample, operations of FIG. 24 may also apply to higher rank (e.g., rank3 or 4) retransmissions where multiple HARQ processes are employed.

FIGS. 25, 26, and 27 are flow charts illustrating operations of basestation processor 101 supporting HARQ feedback, retransmissions, HARQprocess identifications, and discontinuous transmission (DTX) accordingto some embodiments. Operations of FIGS. 25, 26, and 27 may be appliedfor rank 2 and higher MIMO downlink DL transmissions using multiple HARQprocesses/identifications (e.g., HARQ-1/H_a and HARQ-2/H_b). Discussionof rank 1 transmissions may be omitted because discontinuoustransmission may not be applicable to rank 1transmissions/retransmissions.

At block 2501 of FIG. 25, base station processor 101 may provide newdata for two data blocks for a rank 2 transmission, three data blocksfor a rank 3 transmission, or 4 data blocks for a rank 4 transmission.While examples of the following operations may be discussed for two datablocks for rank 2 transmission/retransmission, embodiments herein arealso applicable for higher rank transmissions/retransmissions.

At block 2503, processor 101 may generate and transmit downlink DLsignaling for an initial transmission of the first and second datablocks. Operations of generating downlink signaling are illustrated inFIG. 27. Responsive to the generation of downlink signaling for aninitial transmission at blocks 2701 and 2702, processor 101 may selectan unused HARQ process ID value (e.g., a value of one to eight) to beused as HARQ process ID H_a for HARQ-1 for the first MIMO layer at block2703. At block 2707, processor 101 may select a HARQ process ID valueH-b for HARQ-2 for the second MIMO layer. At block 2725, H_a and H_b maybe provided for the DL signaling of block 2503 of FIG. 25.

At block 2507 of FIG. 25, processor 101 may transmit (throughtransceiver 109 and antenna array 117) the first and second data blocksover the respective first and second MIMO layers to a wireless terminal200 during a first transmission time interval TTI/TFRE. Responsive toreceiving acknowledgement (ACK) messages for both HARQ process IDs H_aand H_b at block 2509, HARQ process IDs H_a and H_b may be destroyed atblock 2541 freeing the HARQ process ID values to be used fortransmission of new data to wireless terminal 200. Receipt of ACKmessages for both HARQ process IDs H_a and H_b indicates successfulreceipt and decoding of the first and second data blocks at wirelessterminal 200 so that retransmission is not needed.

Responsive to receiving an ACK message for one of HARQ-1/H_a orHARQ-2/H_b and receiving a negative acknowledgment (NACK) message foranother of HARQ-1/H_a or HARQ-2/H_b at block 2509 for the first TTI,processor 101 may generate and transmit downlink signaling to wirelessterminal 200 for a second TTI used to retransmit the data block(s)corresponding to the NACK message at block 2511. More particularly, thedownlink signaling may include a discontinuous transmission (DTX)indicator for the MIMO layer(s) corresponding to the ACK and aretransmission data indicator for the MIMO layer(s) corresponding to theNACK.

Operations of generating downlink signaling are illustrated in FIG. 27.Responsive to the generation of downlink signaling for a retransmissionat blocks 2701 and 2702 and selecting discontinuous transmission atblock 2709, processor 101 may reuse the HARQ process/ID for the HARQprocess/ID corresponding to the NACK message at block 2717 or 2721, andprocessor 101 may generate a HARQ discontinuous transmission (DTX)process identification for the HARQ process corresponding to the ACKmessage at block 2719 or 2723. More particularly, the HARQ DTXprocess/ID may be generated as a function of the HARQ process/IDcorresponding to the NACK. If the NACK is for HARQ-1/H_a so that DTX isapplied to HARQ-2/H_b (corresponding to the ACK) at block 2715, H_a maybe reused from the initial transmission at block 2717, and the HARQ-DTXID may be selected as a function of H_a at block 2719. If the NACK isfor HARQ-2 so that DTX is applied to HARQ-1/H_a (corresponding to theACK) at block 2715, H_b may be reused from the initial transmission atblock 2721, and the HARQ-DTX ID may be selected as a function of H_b atblock 2723. At block 2725, the HARQ process/IDs may be provided for theDL signaling of block 2511 of FIG. 25.

At block 2515, processor 101 may retransmit the NACKed data block(s)over the respective MIMO layer(s) during a subsequent TTI/TFRE withoutretransmitting the data block(s) over the MIMO layer(s) corresponding tothe ACK. Stated in other words, discontinuous transmission may beapplied over the MIMO layer(s) corresponding to the ACK. If an ACKmessage is received responsive to the retransmission at block 2517, theHARQ process(es)/ID(s) for the data blocks of block 2501 may bedestroyed at block 2541 thereby freeing the HARQ process ID values to beused for other data blocks. If a NACK message is received responsive tothe retransmission at block 2517, operations of blocks 2511, 2515, and2517 may be repeated until either an ACK is received at block 2517 or amaximum allowed number of retransmissions has occurred at block 2519.Operations of blocks 2511 and 2515 may be similar to and/or the same asthose discussed above with respect blocks 2121 and 2123 of FIG. 19. Ifthe maximum allowed number of retransmission has occurred at block 2519,the HARQ process ID for the data blocks of block 2501 may be destroyedat block 2541 thereby freeing the HARQ process ID values to be used forother data blocks.

Responsive to receiving NACK messages for both HARQ processes/IDs atblock 2509 for the first TTI, processor 101 may determine at block 2521if a subsequent retransmission of all NACKed data blocks is allowed.According to some embodiments, a predetermined number of retransmissions(e.g., two retransmissions) of all NACKed data blocks may be allowed atblock 2521 (indicated by “yes”) before invoking/using discontinuoustransmission DTX. According to other embodiments, discontinuoustransmission may be invoked at block 2521 (indicated by “no”) after theinitial transmission if NACK messages are received for both HARQprocesses/IDs.

If one or more retransmissions of all NACKed data is permitted at block2521, processor 101 may determine at block 2523 if wireless terminal 200has requested a MIMO rank that is reduced relative to the MIMO rank ofthe initial transmission at block 2507. If wireless terminal continuesto request a same or higher MIMO rank (indicating the same or improvedchannel quality) or if no further MIMO rank preference has been receivedfrom wireless terminal 200 since the initial transmission at block 2507,processor 101 may retransmit all NACKed data blocks at blocks 2525 and2527 a predetermined number of times until an ACK/ACKs are received atblock 2509, until a maximum allowed number of retransmissions of alldata occurs at block 2521, or until wireless terminal 200 requests alower MIMO rank (indicating a reduction in channel quality) at block2523.

For each retransmission of all NACKed data (without discontinuoustransmission), processor 101 may generate and transmit downlinksignaling to wireless terminal 200 for a subsequent TTI used toretransmit the data blocks corresponding to the NACK messages at block2525 without discontinuous transmission. Operations of generatingdownlink signaling are illustrated in FIG. 27. Responsive to thegeneration of downlink signaling for a retransmission at blocks 2701 and2702 without discontinuous transmission at block 2709, processor 101 mayreuse HARQ process IDs/values for all HARQ processes/IDs (e.g.,HARQ-1/H_a and HARQ-2/H_b) corresponding to the NACK messages at block2711. More particularly, values of H_a and H_b may be reused from theinitial transmission at block 2711. At block 2725, the HARQ process IDvalues may be provided for the DL signaling of block 2525 of FIG. 25. Atblock 2527 of FIG. 25, processor 101 may retransmit (through transceiver109 and antenna array 117) all NACKed data blocks over the respectiveMIMO layers to wireless terminal 200 during a subsequent transmissiontime interval TTI.

Responsive to retransmitting all data blocks a maximum number of timesat block 2521 and/or responsive to receiving a preference from wirelessterminal 200 for a second MIMO rank less than the first rank at block2523, processor 101 may proceed to operations of FIG. 26 as indicated atblock 2529 of FIG. 25. If the initial transmission of block 2507 was arank 4 transmission with first and fourth data blocks transmitted overrespective first and fourth MIMO layers mapped to HARQ-1/H_a and withsecond and third data blocks transmitted over respective second andthird MIMO layers mapped to HARQ-2/H_b, a reduced rank would be rank 1,2, or 3. If the initial transmission of block 2507 was a rank 3transmission with a first data block transmitted over the first MIMOlayer mapped to HARQ-1/H_a and with second and third data blockstransmitted over respective second and third MIMO layers mapped toHARQ-2/H_b, a reduced rank would be rank 1 or 2. If the initialtransmission of block 2507 was a rank 2 transmission with a first datablock transmitted over the first MIMO layer mapped to HARQ-1/H_a andwith a second data block transmitted over the second MIMO layer mappedto HARQ-2/H_b, a reduced rank would be rank 1.

At block 2601, processor 101 may select a data block(s) and MIMOlayer(s) corresponding to one HARQ process/ID for discontinuoustransmission, and processor 101 may select a data block(s) and MIMOlayer(s) corresponding to the other HARQ process/ID for retransmission.According to some embodiments, processor 101 may select data block(s)and MIMO layer(s) corresponding to the HARQ process/ID providing thegreater spectral efficiency to provide a higher data rate. With rank 3transmission, for example, processor 101 may select data blocks of thesecond and third MIMO layers corresponding to HARQ-2/H_b to provide anincreased data rate relative to the data block of the first MIMO layercorresponding to HARQ-1/H_a. With rank two or rank 4 transmissions withthe same number of data blocks mapped to each HARQ process/ID, processor101 may determine spectral efficiency based on transport block sizesused for the different HARQ processes. According to other embodiments,processor 101 may select data block(s) and MIMO layer(s) correspondingto the HARQ process/ID providing the lesser spectral efficiency toprovide a higher likelihood of successful reception/decoding at wirelessterminal 200.

At block 2603, processor 101 may generate and transmit (throughtransceiver 109 and antenna array 117) downlink signaling to wirelessterminal 200 for a subsequent TTI/TFRE wherein the downlink signalingfor the second TTI/TFRE includes a retransmission data indicator for thedata block(s) and MIMO layer(s) corresponding to the selected HARQprocess and a discontinuous transmission (DTX) indicator for the datablock(s) and MIMO layer(s) corresponding to the non-selected HARQprocess/ID. The downlink signaling may also include a retransmissionindicator for the data block(s) and MIMO layer(s) corresponding to theselected HARQ process/ID. Operations of generating downlink signalingmay be the same as discussed above with respect to blocks 2715, 2717,2719, 2721, 2723, and 2725 of FIG. 27.

At block 2605, processor 101 may retransmit (through transceiver 109 andantenna array 117) the selected data block(s) over the respective MIMOlayer(s) to wireless terminal 200 during the second/subsequent TTI/TFREwithout retransmitting the non-selected data block(s) corresponding tothe non-selected HARQ process/ID. Even though wireless terminal 200 mayhave requested a reduced MIMO rank, the retransmission may maintain theMIMO rank of the initial transmission to maintain a same mapping of theretransmitted data to respective soft buffers of wireless terminal 200.

If an ACK message is received for the retransmission (of block 2605) atblock 2607, processor 101 may transmit (through transceiver 109 andantenna array 117) downlink signaling to wireless terminal 200 for asubsequent TTI/TFRE wherein the downlink signaling for the subsequentTTI/TFRE includes a discontinuous transmission (DTX) indicator for thepreviously selected MIMO layer(s) and data block(s) corresponding to thepreviously selected HARQ process/ID and a retransmission data indicatorfor the previously non-selected MIMO layer(s) and data block(s)corresponding to the previously non-selected HARQ process/ID. Downlinksignaling of block 2609 may be generated as discussed above with respectto blocks 2715, 2717, 2719, 2721, 2723, and 2725.

At block 2611, processor 101 may retransmit (through transceiver 109 andantenna array 117) the previously non-selected data block(s) over thepreviously non-selected MIMO layer corresponding to the previouslynon-selected HARQ process to wireless terminal 200 during the subsequentTTI/TFRE in accordance with the MIMO rank of the initial transmission.If an ACK message is received at block 2615 responsive to theretransmission of block 2611, the HARQ process ID(s) for the data blocksof blocks 2605 and 2611 may be destroyed at block 2541 (of FIG. 25)thereby freeing the HARQ process ID values to be used for other datablocks. If a NACK message is received responsive to the retransmissionat block 2615, operations of blocks 2609, 2611, and 2615 may be repeateduntil either an ACK is received at block 2615 or a maximum allowednumber of retransmissions has occurred at block 2617. Operations ofblocks 2609 and 2611 are similar to and/or the same as those discussedabove with respect to block 2511 and 2515 of FIG. 25 and/or blocks 2121and 2123 of FIG. 19. If the maximum allowed number of retransmission hasoccurred at block 2617, the HARQ process ID(s) for the data blocks ofblocks 2605 and 2611 may be destroyed at block 2541 (of FIG. 25) therebyfreeing the HARQ process ID values to be used for other data blocks.

If NACKs are received for both HARQ processes/IDs at block 2509 of FIG.25, processor 101 may select the data block(s) and MIMO layer(s)corresponding to one of the HARQ processes/IDs for initialretransmission. Retransmission of the non-selected data block(s) andMIMO layer(s) corresponding to the other HARQ process/ID may thus bedelayed until an ACK is received for the selected data block(s). Byreducing the data selected for retransmission when all NACKs arereceived for the initial transmission, a likelihood of success for theretransmission may be increased by reducing multi-antenna interference.

If a NACK message is received for the retransmission (of block 2605) atblock 2607, processor 101 may repeat operations of blocks 2603, 2605,and 2607 either until an ACK message is received for the retransmissionat block 2607 or until a maximum number of retransmissions has occurredat block 2619. If the maximum allowed number of retransmission hasoccurred at block 2619, the HARQ process ID(s) may be destroyed at block2541 (of FIG. 25) thereby freeing the HARQ process ID values to be usedfor other data blocks.

Embodiments discussed herein may thus define use of discontinuoustransmission DTX. If base station (nodeB) processor 101 initiallytransmits first through fourth data blocks over respective first throughfourth MIMO layers during a rank 4 TTI/TFRE at block 2507 of FIG. 25,and if NACKs are received for HARQ-1/H_a (mapped to the first and fourthMIMO layers) and for HARQ-2/H_b (mapped to the second and third MIMOlayers) at block 2509 of FIG. 25, then base station processor 101 mayretransmit all four data blocks up to a maximum number of times atblocks 2521, 2523, 2525, and 2527 until either an ACK is received atblock 2509, a maximum allowed number of retransmissions has occurred atblock 2521, or a reduced MIMO rank is requested by wireless terminal 200at block 2523. If a maximum allowed number of retransmissions (e.g., tworetransmissions for a total of three transmissions/retransmissions)occurs without receiving an ACK for either HARQ-1/H_a or HARQ-2/H_b,HARQ gain may not be useful (as the HARQ gain may be reduced withincreased numbers of retransmissions). Accordingly, discontinuoustransmission DTX for one of the HARQ processes/IDs may be implemented asdiscussed above with respect to FIG. 26.

For example, HARQ-1/H_a (corresponding to the first and fourth datablocks) may be selected for discontinuous transmission DTX at block 2601of FIG. 26, or HARQ-2/H_b (corresponding to the second and third datablocks) may be selected for discontinuous transmission DTX at block 2601of FIG. 26. If HARQ-1/H_a is selected for discontinuous transmission,downlink signaling may include a DTX indicator for HARQ-1/H_a and aretransmission indicator for HARQ-2/H_b at block 2603, and at block2605, the second and third data blocks may be retransmitted over thesecond and third MIMO layers using rank 4 without transmitting over thefirst and fourth MIMO layers. If HARQ-2/H_b is selected fordiscontinuous transmission, downlink signaling may include a DTXindicator for HARQ-2/H_b and a retransmission indicator for HARQ-1/H_aat block 2603, and at block 2605, the first and fourth data blocks maybe retransmitted over the first and fourth MIMO layers using rank 4without transmitting over the second and third MIMO layers. Byretransmitting data blocks of only one HARQ process/ID, multi-antennainterference may be reduced thereby increasing signal quality of theretransmitted data and increasing a probability of successfulreceipt/decoding at wireless terminal 200.

Discontinuous transmission may thus be used when a NACK is received forany one or more of the HARQ processes/IDs. According to someembodiments, discontinuous transmission may be used when an ACK isreceived for a HARQ process/ID and a NACK is received for another HARQprocess/ID as shown by the ACK/NACK output of block 2509 of FIG. 25.According to some embodiments, discontinuous transmission may be usedwhen NACKS are received for all HARQ processes/IDs as shown by the allNACKs output of block 2509 of FIG. 25. If all NACKs are received, anumber of retransmissions of all NACKed data blocks may be allowed atblocks 2521, 2523, 2525, 2527, and 2509 of FIG. 25 before usingdiscontinuous transmission of FIG. 26. If all NACKs are received atblock 2509 according to some other embodiments, processor 101 may usediscontinuous transmission of FIG. 26 for a next retransmission omittingblocks 2521, 2523, 2525, and 2527 of FIG. 25.

If base station (node B) processor 101 initially transmits first throughfourth data blocks over respective first through fourth MIMO layersduring a rank 4 TTI/TFRE at block 2507 of FIG. 25, and if NACKs arereceived for HARQ-1/H_a and for HARQ-2/H_b at block 2509 of FIG. 25,then base station processor 101 may retransmit all four data blocks upto a maximum number of times at blocks 2521, 2523, 2525, and 2527 asdiscussed above, as long as wireless terminal 200 does not request areduced MIMO rank (e.g., MIMO rank 1, 2, or 3). If wireless terminal 200requests a reduced MIMO rank (indicating reduced downlink channelquality) at block 2523, base station processor 101 may use discontinuoustransmission of FIG. 26. According to some embodiments, discontinuoustransmission may be used for a retransmission responsive to any or allNACKs (e.g., if an ACK is received for one HARQ process/ID and a NACK isreceived for the other HARQ process/ID, or if NACKs are received for allHARQ processes/IDs) any time wireless terminal 200 requests a reducedMIMO rank. Discontinuous transmission may thus be used if the wirelessterminal currently preferred MIMO rank is less than the MIMO rank of theinitial transmission.

Base station (node B) processor 101 may initially transmit multiple datablocks using multiple HARQ processes/IDs, for example, using MIMO rank 2(transmitting first and second data blocks over first and second MIMOlayers), MIMO rank 3 (transmitting first, second, and third data blocksover first, second, and third MIMO layers), or MIMO rank 4 (transmittingfirst, second, third, and fourth data blocks over first, second, third,and fourth MIMO layers). As discussed above with respect to blocks 2107,2121, and 2123 of FIG. 19, if base station processor 101 is transmitbuffer limited with respect to wireless terminal 200 (e.g., there isno/insufficient data for a new data block for transmission to wirelessterminal 200), discontinuous transmission may be used for the MIMOlayer(s) corresponding to the ACK during the retransmission of datablocks corresponding to the NACK.

According to some embodiments, a HARQ process identification may beprovided for a DTX codeword. In a four branch MIMO system (includingfour transmit and four receive antennas supporting up to four MIMOlayers), HARQ process identifications may be defined for each transportdata block. For example, first HARQ process identification H_a may beprovided for first HARQ process HARQ-1 that is mapped to the first MIMOlayer for ranks 1, 2, and 3 and to first and fourth MIMO layers for rank4, and second HARQ process identification H_b may be provided for secondHARQ process HARQ-2 that is mapped to the second MIMO layer for rank 2and to the second and third MIMO layers for ranks 3 and 4. Moreover,values of HARQ process identifications H_a and H_b may be relatedaccording to the following equation:H_b=(H_a+N/2)mod(N),where N is a number of HARQ processes that may be configured forwireless terminal 200 by higher layers of base station 100 or radionetwork controller. Because H_b may be determined from H_a, onlyinformation relating to H_a may need to be transmitted from base station100 to wireless terminal 200. Wireless terminal 200 may thus receive H_aand then derive H_b according to the formula discussed above.

If discontinuous transmission is used for a retransmission, the HARQprocess identification for the DTXed HARQ process may be determined asfollows. If discontinuous transmission is applied to HARQ-2 (e.g., ifNACK was received for HARQ-1 and ACK was received for HARQ-2, or ifHARQ-2 is selected for DTX after receiving both NACKs), then the HARQprocess ID value for the DTX may be provided as:HARQ_DTX=(H_a _(old) +N/2)mod(N),where H_a_(old) is the HARQ process ID value of HARQ-1 that was NACKedin the previous transmission. Stated in other words, if DTX is appliedto HARQ-2 during a retransmission (with two HARQ processes and 8 HARQprocess ID values), the HARQ_DTX identification for the retransmissionmay be derived from H_a_(old) according to the following table (whereH_a_(old) is the HARQ process ID of HARQ-1 during the previoustransmission):

H_a_(old) HARQ_DTX 1 5 2 6 3 7 4 8 5 1 6 2 7 3 8 4

If discontinuous transmission is applied to HARQ-1 (e.g., if ACK wasreceived for HARQ-1 and NACK was received for HARQ-2, or if HARQ-1 isselected for DTX after receiving both NACKs), then the HARQ process IDfor the DTX may be provided as:HARQ_DTX=H_b _(old) +K*N/2,where H_b_(old) is the HARQ process ID of HARQ-2 that was NACKed in theprevious transmission, where K=−1 if H_b_(old)>N/2, and where K=+1 ifH_b_(old)≦N/2. Stated in other words, if DTX is applied to HARQ-1 duringa retransmission (with two HARQ processes and 8 HARQ process ID values),the HARQ_DTX identification for the retransmission may be derived fromH_b_(old) according to the following table (where H_b_(old) is the HARQprocess ID of HARQ-2 during the previous transmission):

H_b_(old) HARQ_DTX 1 5 2 6 3 7 4 8 5 1 6 2 7 3 8 4These HARQ process identifications for HARQ_DTX may be unique and may bethe only solution to implement a DTX codeword and/or identification.

According to some embodiments, when a DTX codeword/indicator is sent towireless terminal 200, wireless terminal 200 may generate an ACK for theDTX codeword. In this case, base station processor 101 should expect anACK response for the DTX HARQ process, and base station processor 101may destroy the HARQ process/ID for the DTX codeword. If DTX is requiredfor another retransmission, the HARQ_DTX ID may be regenerated asdiscussed above. According to other embodiments, when a DTXcodeword/indicator is sent to wireless terminal 200, wireless terminal200 may generate a NACK for the DTX codeword. In this case, base stationprocessor 101 should also assume that an ACK is received and destroy theHARQ process/ID for the DTX codeword. As before, if DTX is required foranother retransmission, the HARQ_DTX ID may be regenerated as discussedabove.

According to some embodiments, a DTX codeword/ID can be used when one ofthe codewords/HARQ processes fails (i.e., generates an ACK) and anotherof the codewords/HARQ processes passes (i.e., generates a NACK).According to some embodiments, a DTX codeword/ID can be used when bothcodewords/HARQ processes fail (i.e., generate NACKs). According to someembodiments, a DTX codeword/ID can be used when both codewords/HARQprocesses fail (i.e., generate NACKs) for multipletransmission/retransmissions. According to some embodiments, a DTXcodeword can be used when a current wireless terminalpreferred/requested MIMO rank is less than the MIMO rank of theinitial/previous transmission.

According to some embodiments, when using discontinuous transmission forMIMO layers corresponding to one HARQ process, a HARQ process ID for thediscontinuous transmission may be determined as a function of theprevious HARQ process ID for the other HARQ process. If discontinuoustransmission is applied to HARQ-1, for example, the HARQ process ID forthe discontinuous transmission may be determined according to thefollowing formula:HARQ_DTX=H_b _(old) +K*N/2,where H_b_(old) is the HARQ process ID of HARQ-2 from theinitial/previous transmission, where K=−1 if H_b_(old)>N/2, and whereK=+1 if H_b_(old)≦N/2. If discontinuous transmission is applied toHARQ-2, the HARQ process ID for the discontinuous transmission may bedetermined according to the following formula:HARQ_DTX=(H_a _(old) +N/2)mod(N),where H_a_(old) is the HARQ process ID of HARQ-1 from theinitial/previous transmission.

According to some embodiments, when a discontinuous transmission isapplied to codeword and/or HARQ process, base station processor 101 mayassume that an ACK is received for the discontinuous transmission anddestroy the HARQ process/ID irrespective of the HARQ feedbackinformation actually received from wireless terminal 200 over thefeedback channel.

The following numbered embodiments are provided by way of examplewithout limiting the scope of the present application.

Embodiment 1. A method of operating a node (100) of a radio accessnetwork, the method comprising: transmitting (2507) first and seconddata blocks from the radio access network over respective first andsecond multiple-input-multiple-output (MIMO) layers of a MIMO wirelesschannel to a wireless terminal (200) during a first transmission timeinterval (TTI); responsive to receiving an acknowledgment (ACK) messagefor the first data block and a negative acknowledgment (NACK) messagefor the second data block, transmitting (2511) downlink signaling for asecond TTI from the radio access network to the wireless terminal (200)wherein the downlink signaling includes a discontinuous transmission(DTX) indicator for the first MIMO layer and a retransmission dataindicator for the second MIMO layer; and responsive to receiving theacknowledgment (ACK) message for the first data block and the negativeacknowledgment (NACK) message for the second data block, retransmitting(2515) the second data block from the radio access network over thesecond MIMO layer to the wireless terminal (200) during a second TTI.

Embodiment 2. The method according to Embodiment 1 whereinretransmitting the second data block during the second TTI comprisesretransmitting the second data block without transmitting data over thefirst MIMO layer during the second TTI.

Embodiment 3. The method according to any one of Embodiments 1 or 2further comprising: before transmitting the first and second data blocksduring the first transmission time interval, selecting (2703, 2707)first and second HARQ process identifications for the first and secondMIMO layers; and before transmitting the downlink signaling for thesecond TTI, generating (2719, 2723) a HARQ-DTX process identificationfor the first MIMO layer as a function of the second HARQ processidentification for the second MIMO layer.

Embodiment 4. A method of operating a node (100) of a radio accessnetwork, the method comprising: transmitting (2507) first and seconddata blocks from the radio access network over respective first andsecond multiple-input-multiple-output (MIMO) layers of a MIMO wirelesschannel to a wireless terminal (200) during a first transmission timeinterval (TTI); responsive to receiving first and second negativeacknowledgment (NACK) messages for the first and second data blocks,transmitting (2603) downlink signaling from the radio access network tothe wireless terminal (200) for a second TTI wherein the downlinksignaling for the second TTI includes a discontinuous transmission (DTX)indicator for the first MIMO layer and a retransmission data indicatorfor the second MIMO layer; and responsive to receiving the first andsecond negative acknowledgment (NACK) messages for the first and seconddata blocks, retransmitting (2605) the second data block from the radioaccess network over the second MIMO layer to the wireless terminal (200)during the second TTI.

Embodiment 5. The method according to Embodiment 4 whereinretransmitting the second data block during the second TTI comprisesretransmitting the second data block without transmitting data over thefirst MIMO layer during the second TTI.

Embodiment 6. The method according to any one of Embodiments 4 or 5further comprising: responsive to receiving an acknowledgment (ACK)message for the retransmission of the second data block during thesecond TTI, transmitting (2609) downlink signaling from the radio accessnetwork to the wireless terminal (200) for a third TTI wherein thedownlink signaling for the third TTI includes a discontinuoustransmission (DTX) indicator for the second MIMO layer and aretransmission data indicator for the first MIMO layer; and responsiveto receiving the acknowledgment (ACK) message for the retransmission ofthe second data block during the second TTI, retransmitting (2611) thefirst data block from the radio access network over the first MIMO layerto the wireless terminal (200) during the third TTI.

Embodiment 7. The method according to any one of Embodiments 4-6 furthercomprising: before transmitting the first and second data blocks duringthe first transmission time interval, selecting (2703, 2707) first andsecond HARQ process identifications for the first and second MIMOlayers; and before transmitting the downlink signaling for the secondTTI, generating (2719, 2723) a HARQ-DTX process identification for thefirst MIMO layer as a function of the second HARQ process identificationfor the second MIMO layer.

Embodiment 8. A method of operating a node (100) of a radio accessnetwork, the method comprising: transmitting (2507) first and seconddata blocks from the radio access network over respective first andsecond multiple-input-multiple-output (MIMO) layers of a MIMO wirelesschannel to a wireless terminal (200) during a first transmission timeinterval in accordance with a first MIMO rank; responsive to receiving anegative acknowledgment (NACK) message for the first data block andreceiving a preference for a second MIMO rank less than the first rank,transmitting (2603) downlink signaling from the radio access network tothe wireless terminal (200) for a second TTI wherein the downlinksignaling for the second TTI includes a retransmission data indicatorfor the first MIMO layer and a discontinuous transmission (DTX)indicator for the second MIMO layer; and responsive to receiving thenegative acknowledgment (NACK) message for the first data block andreceiving the preference for a second MIMO rank less than the firstrank, retransmitting (2605) the first data block from the radio accessnetwork over the first MIMO layer to the wireless terminal (200) duringthe second TTI in accordance with the first MIMO rank.

Embodiment 9. The method of Embodiment 8 wherein transmitting thedownlink signaling comprises transmitting the downlink signalingresponsive to receiving the negative acknowledgment (NACK) message forthe first data block, receiving a negative acknowledgment (NACK) for thesecond data block, and receiving the preference for the second MIMO rankless than the first rank.

Embodiment 10. The method of embodiment 9 further comprising: responsiveto receiving an acknowledgment (ACK) message for the retransmission ofthe first data block during the second TTI, transmitting (2609) downlinksignaling from the radio access network to the wireless terminal (200)for a third TTI wherein the downlink signaling for the third TTIincludes a discontinuous transmission (DTX) indicator for the first MIMOlayer and a retransmission data indicator for the second MIMO layer; andresponsive to receiving the acknowledgment (ACK) message for theretransmission of the first data block during the second TTI,retransmitting (2611) the second data block from the radio accessnetwork over the second MIMO layer to the wireless terminal (200) duringthe third TTI in accordance with the first MIMO rank.

Embodiment 11. The method according to any one of Embodiments 8-10further comprising: before transmitting the first and second data blocksduring the first transmission time interval, selecting (2703, 2707)first and second HARQ process identifications for the first and secondMIMO layers; and before transmitting the downlink signaling for thesecond TTI, generating (2719, 2723) a HARQ-DTX process identificationfor the second MIMO layer as a function of the first HARQ processidentification for the first MIMO layer.

Embodiment 12. A method of operating a node (100) of a radio accessnetwork, the method comprising: selecting (2703, 2707) first and secondHARQ process identifications for first and second MIMO layers;responsive to selecting the first and second HARQ processidentifications, transmitting (2503) downlink signaling from the radioaccess network to the wireless terminal (200) for a first transmissiontime interval (TTI); transmitting (2507) first and second data blocksfrom the radio access network over respective first and secondmultiple-input-multiple-output (MIMO) layers of a MIMO wireless channelto a wireless terminal (200) during the first TTI; responsive toreceiving a negative acknowledgment (NACK) message for the first datablock, generating (2719, 2723) a HARQ discontinuous transmission (DTX)process identification for the second MIMO layer as a function of thefirst HARQ process identification for the first MIMO layer; responsiveto generating the HARQ-DTX process identification and receiving the NACKmessage for the first data block, transmitting (2603) downlink signalingfrom the radio access network to the wireless terminal (200) for asecond TTI wherein the downlink signaling for the second TTI includes aretransmission data indicator for the first MIMO layer and adiscontinuous transmission (DTX) indicator for the second MIMO layer;and responsive to generating the HARQ-DTX process identification andreceiving the NACK message for the first data block, retransmitting(2605) the first data block from the radio access network over the firstMIMO layer to the wireless terminal (200) during the second TTI.

Acronyms/Abbreviations:

-   -   Tx Transmitter    -   HSDPA High Speed Downlink Packet Access    -   HARQ Hybrid Automatic Repeat Request    -   CRC Cyclic Redundancy Check    -   NAK/NACK Non-Acknowledgment or Negative-Acknowledgment    -   ACK Acknowledgment    -   CC Chase Combining    -   IR Incremental Redundancy    -   UE User Equipment or Wireless Terminal    -   CQI Channel Quality Information    -   MMSE Minimum Mean Square Error    -   TTI Transmit Time Interval    -   PCI Precoding Control Index    -   DTX Discontinuous Transmission

In the above-description of various embodiments, it is to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only and is not intended to be limiting ofpresent inventive concepts. Unless otherwise defined, all terms(including technical and scientific terms) used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich these inventive concepts belong. It will be further understoodthat terms, such as those defined in commonly used dictionaries, shouldbe interpreted as having a meaning that is consistent with their meaningin the context of this specification and the relevant art and will notbe interpreted in an idealized or overly formal sense expressly sodefined herein.

When an element is referred to as being “connected”, “coupled”,“responsive”, or variants thereof to another element, it can be directlyconnected, coupled, or responsive to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected”, “directly coupled”, “directly responsive”,or variants thereof to another element, there are no interveningelements present. Like numbers refer to like elements throughout.Furthermore, “coupled”, “connected”, “responsive”, or variants thereofas used herein may include wirelessly coupled, connected, or responsive.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Well-known functions or constructions may not be described indetail for brevity and/or clarity. The term “and/or” includes any andall combinations of one or more of the associated listed items.

As used herein, the terms “comprise”, “comprising”, “comprises”,“include”, “including”, “includes”, “have”, “has”, “having”, or variantsthereof are open-ended, and include one or more stated features,integers, elements, steps, components or functions but does not precludethe presence or addition of one or more other features, integers,elements, steps, components, functions or groups thereof. Furthermore,as used herein, the common abbreviation “e.g.”, which derives from theLatin phrase “exempli gratia,” may be used to introduce or specify ageneral example or examples of a previously mentioned item, and is notintended to be limiting of such item. The common abbreviation “i.e.”,which derives from the Latin phrase “id est,” may be used to specify aparticular item from a more general recitation.

It will be understood that although the terms first, second, third, etc.may be used herein to describe various elements/operations, theseelements/operations should not be limited by these terms. These termsare only used to distinguish one element/operation from anotherelement/operation. Thus a first element/operation in some embodimentscould be termed a second element/operation in other embodiments withoutdeparting from the teachings of present inventive concepts. Examples ofembodiments of aspects of present inventive concepts explained andillustrated herein include their complimentary counterparts. The samereference numerals or the same reference designators denote the same orsimilar elements throughout the specification.

Example embodiments are described herein with reference to blockdiagrams and/or flowchart illustrations of computer-implemented methods,apparatus (systems and/or devices) and/or computer program products. Itis understood that a block of the block diagrams and/or flowchartillustrations, and combinations of blocks in the block diagrams and/orflowchart illustrations, can be implemented by computer programinstructions that are performed by one or more computer circuits. Thesecomputer program instructions may be provided to a processor circuit ofa general purpose computer circuit, special purpose computer circuit,and/or other programmable data processing circuit to produce a machine,such that the instructions, which execute via the processor of thecomputer and/or other programmable data processing apparatus, transformand control transistors, values stored in memory locations, and otherhardware components within such circuitry to implement thefunctions/acts specified in the block diagrams and/or flowchart block orblocks, and thereby create means (functionality) and/or structure forimplementing the functions/acts specified in the block diagrams and/orflowchart block(s).

These computer program instructions may also be stored in a tangiblecomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks.

A tangible, non-transitory computer-readable medium may include anelectronic, magnetic, optical, electromagnetic, or semiconductor datastorage system, apparatus, or device. More specific examples of thecomputer-readable medium would include the following: a portablecomputer diskette, a random access memory (RAM) circuit, a read-onlymemory (ROM) circuit, an erasable programmable read-only memory (EPROMor Flash memory) circuit, a portable compact disc read-only memory(CD-ROM), and a portable digital video disc read-only memory(DVD/BlueRay).

The computer program instructions may also be loaded onto a computerand/or other programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer and/or otherprogrammable apparatus to produce a computer-implemented process suchthat the instructions which execute on the computer or otherprogrammable apparatus provide steps for implementing the functions/actsspecified in the block diagrams and/or flowchart block or blocks.Accordingly, embodiments of present inventive concepts may be embodiedin hardware and/or in software (including firmware, resident software,micro-code, etc.) that runs on a processor such as a digital signalprocessor, which may collectively be referred to as “circuitry,” “amodule” or variants thereof.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Finally, other blocks maybe added/inserted between the blocks that are illustrated, and/orblocks/operations may be omitted without departing from the scope ofpresent inventive concepts. Moreover, although some of the diagramsinclude arrows on communication paths to show a primary direction ofcommunication, it is to be understood that communication may occur inthe opposite direction to the depicted arrows.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of variousexample combinations and subcombinations of embodiments and of themanner and process of making and using them, and shall support claims toany such combination or subcombination.

Many variations and modifications can be made to the embodiments withoutsubstantially departing from principles of present inventive concepts.All such variations and modifications are intended to be included hereinwithin the scope of present inventive concepts. Accordingly, the abovedisclosed subject matter is to be considered illustrative, and notrestrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe spirit and scope of present inventive concepts. Thus, to the maximumextent allowed by law, the scope of present inventive concepts are to bedetermined by the broadest permissible interpretation of the appendedclaims, and shall not be restricted or limited by the foregoing detaileddescription.

That which is claimed is:
 1. A method of operating a node of a radioaccess network, the method comprising: selecting first and second HARQprocess identifications for first and secondmultiple-input-multiple-output (MIMO) layers of a MIMO wireless channel;transmitting first and second data blocks from the radio access networkrespectively over the first and second MIMO layers of the MIMO wirelesschannel to a wireless terminal during a first transmission time interval(TTI); responsive to receiving a negative acknowledgment (NACK) messagefor the second data block, generating a HARQ discontinuous transmission(HARQ-DTX) process identification for the first MIMO layer as a functionof the second HARQ process identification for the second MIMO layer;responsive to receiving the NACK message for the second data block,transmitting downlink signaling for a second TTI from the radio accessnetwork to the wireless terminal wherein the downlink signaling includesa discontinuous transmission (DTX) indicator for the first MIMO layerand a retransmission data indicator for the second MIMO layer, whereinthe downlink signaling for the second TTI including the DTX indicatorand the retransmission data indicator is transmitted using a downlinksignaling channel; and responsive to receiving the NACK message for thesecond data block, retransmitting the second data block from the radioaccess network over the second MIMO layer to the wireless terminalduring the second TTI, wherein the second data block is retransmittedover the second MIMO layer using a downlink traffic channel.
 2. Themethod of claim 1 wherein transmitting the downlink signaling comprisestransmitting the downlink signaling responsive to receiving anacknowledgment (ACK) message for the first data block and responsive toreceiving the NACK message for the second data block, and whereinretransmitting the second data block comprises retransmitting the seconddata block responsive to receiving the ACK message for the first datablock and responsive to receiving the NACK message for the second datablock.
 3. The method of claim 1 wherein retransmitting the second datablock during the second TTI comprises retransmitting the second datablock without transmitting data over the first MIMO layer during thesecond TTI.
 4. The method of claim 1: wherein transmitting the first andsecond data blocks during the first transmission time interval (TTI)comprises transmitting the first and the second data blocks afterselecting the first and second HARQ process identifications for thefirst and second MIMO layers; and wherein transmitting the downlinksignaling for the second, TTI comprises transmitting the downlinksignaling for the second TTI after generating the HARQ-DTX processidentification for the first MIMO layer.
 5. The method according toclaim 1 further comprising: responsive to selecting the first and secondHARQ process identifications, transmitting downlink signaling from theradio access network to the wireless terminal for the first transmissiontime interval (TTI); wherein transmitting the downlink signaling for thesecond TTI comprises transmitting the downlink signaling for the secondTTI responsive to generating the HARQ-DTX process identification andresponsive to receiving the NACK message for the second data block, andwherein retransmitting the second data block comprises retransmittingthe second data block responsive to generating the HARQ-DTX processidentification and responsive to receiving the NACK message for thesecond data block.
 6. The method of claim 1 wherein the downlinksignaling channel is a High Speed Shared Control Channel (HS-SCCH), andwherein the downlink traffic channel is a High Speed Physical DownlinkShared Channel (HS-PDSCH).
 7. A method of operating a node of a radioaccess network, the method comprising: transmitting first and seconddata blocks from the radio access network over respective first andsecond multiple-input-multiple-output (MIMO) layers of a MIMO wirelesschannel to a wireless terminal during a first transmission time interval(TTI); responsive to receiving a negative acknowledgment (NACK) messagefor the first data block and a NACK message for the second data block,transmitting downlink signaling for a second TTI from the radio accessnetwork to the wireless terminal wherein the downlink signaling includesa discontinuous transmission (DTX) indicator for the first MIMO layerand a retransmission data indicator for the second MIMO layer; andresponsive to receiving the NACK message for the first data block andthe NACK message for the second data block, retransmitting the seconddata block from the radio access network over the second MIMO layer tothe wireless terminal during the second TTI.
 8. The method of claim 7wherein retransmitting the second data block during the second TTIcomprises retransmitting the second data block without transmitting dataover the first MIMO layer during the second TTI.
 9. The method of claim7 further comprising: responsive to receiving an acknowledgment (ACK)message for the retransmission of the second data block during thesecond TTI, transmitting downlink signaling from the radio accessnetwork to the wireless terminal for a third TTI wherein the downlinksignaling for the third TTI includes a discontinuous transmission (DTX)indicator for the second MIMO layer and a retransmission data indicatorfor the first MIMO layer; and responsive to receiving the ACK messagefor the retransmission of the second data block during the second TTI,retransmitting the first data block from the radio access network overthe first MIMO layer to the wireless terminal during the third TTI. 10.The method of claim 7 further comprising: before transmitting the firstand second data blocks during the first transmission time interval,selecting first and second HARQ process identifications for the firstand second MIMO layers; and before transmitting the downlink signalingfor the second TTI, generating a HARQ-DTX process identification for thefirst MIMO layer as a function of the second HARQ process identificationfor the second MIMO layer.
 11. A method of operating a node of a radioaccess network, the method comprising: transmitting first and seconddata blocks from the radio access network over respective first andsecond multiple-input-multiple-output (MIMO) layers of a MIMO wirelesschannel to a wireless terminal during a first transmission time interval(TTI) in accordance with a first MIMO rank; responsive to receiving anegative acknowledgment (NACK) message for the second data block andresponsive to receiving a preference for a second MIMO rank less thanthe first MIMO rank from the wireless terminal, transmitting downlinksignaling for a second TTI from the radio access network to the wirelessterminal wherein the downlink signaling includes a discontinuoustransmission (DTX) indicator for the first MIMO layer and aretransmission data indicator for the second MIMO layer; and responsiveto receiving the NACK message for the second data block and responsiveto receiving the preference for the second MIMO rank less than the firstMIMO rank, retransmitting the second data block from the radio accessnetwork over the second MIMO layer to the wireless terminal during thesecond TTI in accordance with the first MIMO rank.
 12. The method ofclaim 11 wherein transmitting the downlink signaling comprisestransmitting the downlink signaling responsive to receiving a NACK forthe first data block, responsive to receiving the NACK message for thesecond data block, and responsive to receiving the preference for thesecond MIMO rank less than the first rank.
 13. The method of claim 12wherein retransmitting the second data block during the second TTIcomprises retransmitting the second data block without transmitting dataover the first MIMO layer during the second TTI.
 14. The method of claim11 further comprising: responsive to receiving an acknowledgment (ACK)message for the retransmission of the second data block during thesecond TTI, transmitting downlink signaling from the radio accessnetwork to the wireless terminal for a third TTI wherein the downlinksignaling for the third TTI includes a retransmission data indicator forthe first MIMO layer and a discontinuous transmission (DTX) indicatorfor the second MIMO layer; and responsive to receiving theacknowledgment (ACK) message for the retransmission of the second datablock during the second TTI, retransmitting the first data block fromthe radio access network over the second MIMO layer to the wirelessterminal during the third TTI in accordance with the first MIMO rank.15. The method according to claim 11 further comprising: beforetransmitting the first and second data blocks during the firsttransmission time interval, selecting first and second HARQ processidentifications for the first and second MIMO layers; and beforetransmitting the downlink signaling for the second TTI, generating aHARQ-DTX process identification for the first MIMO layer as a functionof the second HARQ process identification for the second MIMO layer. 16.A node of a radio access network, the node comprising: a transceiverconfigured to communicate with a wireless terminal over amultiple-input-multiple-output (MIMO) wireless channel; and a processorcoupled to the transceiver, wherein the processor is configured to,select first and second HARQ process identifications for first andsecond MIMO layers of the MIMO wireless channel; transmit first andsecond data blocks through the transceiver respectively over the firstand second MIMO layers of the MIMO wireless channel to a wirelessterminal during a first transmission time interval (TTI), generate aHARQ discontinuous transmission (HARQ-DTX) process identification forthe first MIMO layer as a function of the second HARQ processidentification for the second MIMO layer responsive to receiving anegative acknowledgment (NACK) message for the second data block;transmit downlink signaling for a second TTI through the transceiver tothe wireless terminal responsive to receiving the NACK message for thesecond data block, wherein the downlink signaling includes adiscontinuous transmission (DTX) indicator for the first MIMO layer anda retransmission data indicator for the second MIMO layer, wherein thedownlink signaling for the second TTI including the DTX indicator andthe retransmission data indicator is transmitted using a downlinksignaling channel, and retransmit the second data block through thetransceiver over the second MIMO layer to the wireless terminal duringthe second TTI responsive to receiving the NACK message for the seconddata block, wherein the second data block is retransmitted over thesecond MIMO layer using a downlink traffic channel.
 17. The node ofclaim 16 wherein the processor is configured to transmit the downlinksignaling responsive to receiving an acknowledgment (ACK) message forthe first data block and responsive to receiving the NACK message forthe second data block, and wherein the processor is configured toretransmit the second data block responsive to receiving the ACK messagefor the first data block and responsive to receiving the NACK messagefor the second data block.
 18. The node of claim 16 wherein theprocessor is further configured to, transmit downlink signaling from theradio access network to the wireless terminal for the first TTIresponsive to selecting the first and second HARQ processidentifications, wherein transmitting the downlink signaling for thesecond TTI comprises transmitting the downlink signaling for the secondTTI responsive to generating the HARQ-DTX process identification andresponsive to receiving the NACK message for the second data block, andwherein retransmitting the second data block comprises retransmittingthe second data block responsive to generating the HARQ-DTX processidentification and responsive to receiving the NACK message for thesecond data block.
 19. The node of claim 16 wherein the processor isconfigured to retransmit the second data block without transmitting dataover the first MIMO layer during the second TTI.
 20. The node of claim16 wherein the downlink signaling channel is a High Speed Shared ControlChannel (HS-SCCH), and wherein the downlink traffic channel is a HighSpeed Physical Downlink Shared Channel (HS-PDSCH).
 21. A node of a radioaccess network, the node comprising: a transceiver configured tocommunicate with a wireless terminal over amultiple-input-multiple-output (MIMO) wireless channel; and a processorcoupled to the transceiver, wherein the processor is configured to,transmit first and second data blocks through the transceiver overrespective first and second MIMO layers of the MIMO wireless channel toa wireless terminal during a first transmission time interval (TTI),transmit downlink signaling for a second TTI through the transceiver tothe wireless terminal responsive to receiving a negative acknowledgment(NACK) message for the first data block and a NACK message for thesecond data block, wherein the downlink signaling includes adiscontinuous transmission (DTX) indicator for the first MIMO layer anda retransmission data indicator for the second MIMO layer, andretransmit the second data block through the transceiver over the secondMIMO layer to the wireless terminal during the second TTI responsive toreceiving the NACK message for the first data block and the NACKmessages for the second data block.
 22. The node of claim 21 wherein theprocessor is configured to retransmit the second data block during thesecond TTI by retransmitting the second data block without transmittingdata over the first MIMO layer during the second TTI.
 23. A node of aradio access network, the node comprising: a transceiver configured tocommunicate with a wireless terminal over amultiple-input-multiple-output (MIMO) wireless channel; and a processorcoupled to the transceiver, wherein the processor is configured to,transmit first and second data blocks through the transceiver overrespective first and second MIMO layers of the MIMO wireless channel toa wireless terminal in accordance with a first MIMO rank during a firsttransmission time interval (TTI), transmit downlink signaling for asecond TTI through the transceiver to the wireless terminal responsiveto receiving a negative acknowledgement (NACK) message for the seconddata block and responsive to receiving a preference for a second MIMOrank less than the first rank from the wireless terminal, wherein thedownlink signaling includes a discontinuous transmission (DTX) indicatorfor the first MIMO layer and a retransmission data indicator for thesecond MIMO layer, and retransmit the second data block through thetransceiver over the second MIMO layer to the wireless terminal duringthe second TTI in accordance with the first MIMO rank responsive toreceiving the NACK message for the second data block and responsive toreceiving the NACK message for the second data block and responsive toreceiving the preference for the second MIMO rank less than the firstMIMO rank.
 24. The node of claim 23 wherein the processor is furtherconfigured to transmit the downlink signaling responsive to receiving aNACK for the first data block, responsive to receiving the NACK messagefor the second data block, and responsive to receiving the preferencefor the second MIMO rank less than the first rank.